Hoval Rotary Heat Exchangerfor Heat Recovery in Ventilation Systems.

Casing for installation in air handling units or

for duct connection

Storage mass consisting of pure aluminium or coated with sorbent

Hub with long-lasting and long service life inner ball bearings

Purge sector prevents contamination of supply air by extract air

Three-phase drive motor with belt pulley and V-belt, continuously controllable

Low leakage thanks to high-quality peripheral slide seal

Rigid and long-lasting spokes

construction

Adjustable transverse seal

with a 3-lip rubber seal

1

9 Commissioning and maintenance _______________23

9.1 Commissioning9.2 Maintenance

10 Design considerations _______24

10.1 Data collection10.2 Rules and guidelines10.3 Positioning of units10.4 Wheel type10.5 Cost-effective design10.6 Performance control10.7 Bypass10.8 Frost limit10.9 Use and sizing of the purge sector10.10 Internal leakage10.11 Pressure difference10.12 Cross-contamination10.13 Supply air humidification10.14 Corrosion10.15 Application limits10.16 Clogging10.17 Condensation in the warm air stream10.18 Exchanger selection10.19 Technical data

11 Specification texts __________27

11.1 Condensation wheel11.2 Sorption wheel

12 Order form ________________28

Table of Contents

Hoval Rotary Heat ExchangersHandbook for Design, Installation and Operation

Subject to technical alterations.Art.Nr. 4 208 534 – 04 / 2009© Hovalwerk AG, Liechtenstein, 2005, 2007, 2008, 2009

1 Principle of operation __________2

1.1 Heat transfer1.2 Moisture transfer1.3 Leakage1.4 Frost limit1.5 Heat recovery efficiency1.6 Pressure drop1.7 Pressure difference

2 Performance control __________7

3 Construction _________________8

3.1 Rotor3.2 Casing3.3 Drive

4 Options ___________________12

4.1 Drive motor A4.2 Control unit R4.3 Operating unit B4.4 Motion detection D4.5 Purge sector S4.6 Inspection port I

5 Unit type reference __________16

6 Design calculation ___________18

6.1 Design data6.2 Selection program Hoval CAPS6.3 Performance chart6.4 Tested data

7 Dimensions and weights ______20

8 Transport and installation ______22

8.1 Transportation8.2 Mechanical installation8.3 Condensate drain connection8.4 Fitting of sensors8.5 Electrical connection8.6 Assembly of segmented rotary heat

exchangers8.7 Horizontal installation

2

Principle of operation

Principle of operation1

Within the guidelines for heat recovery (e.g. VDI 2071) Hoval rotary heat exchangers are classified as regenerators with rotating heat carrier (category 3). In a counterflow arrange-ment, the rotating, air permeable storage mass is heated and cooled alternately by the heat releasing and heat absorbing air streams. Depending on the air conditions and on the surface of the storage mass also moisture may be transferred in this process. The supply and extract air streams must be adjacent and pass through the heat ex-changer simultaneously.The storage mass is formed of narrow, triangular air chan-nels in axial direction, consisting of thin metal foil. The depth of the storage mass (in the direction of air flow) usu ally is 200 mm; the airway height is generally 1.6 – 2.9 mm, de-pending on the application. With these dimensions a laminar flow through the air channels results.

Fresh airt21x21

Supply airt22x22

Exhaust airt12x12

Extract airt11x11

Principle of operation and air conditionsFig. 1:

Geometry of the storage Fig. 2: mass

Heat transfer1.1 The rotor with its axial, smooth air channels serves as a storage mass, half of which is heated by the warm air stream and half of which is cooled by the cold air stream, in a counterflow arrangement. Consequently, the temperature of the storage mass varies depending on the axial co ordinate (rotor depth) and on the angle of rotation.The principle of operation is easy to understand by following the condition of an air channel during one revolution (see figure 3). From this process, the following can be seen:

The air temperature at the exchanger outlet is not uni- ●form; it depends on the angle of rotation.The heat recovery efficiency may be influenced by adjust- ●ing the speed of rotation.The heat recovery efficiency may also be influenced via ●the storage mass: wider or narrower air channels, differ-ent thickness of the storage material, other rotor depth. Pressure drop will also be affected.The specific heat output capacity depends on the tem- ●perature difference between the two air streams. Hence the rotary heat exchanger is suitable for heat as well as cool recovery, i.e. for winter and summer operation.

Definition of key figures according to VDI 2071

Heat recovery figure of cold air t22 -  t21 Φ2  =  t11 - t21

Moisture recovery figure of cold air x22 - x21 Ψ2  =  x11 - x21

Legend:

t = Air temperature [K; °C]x = Absolute humidity [g/kg]

1st Index: 1 Warm air 2 Cold air

2nd Index: 1 Exchanger inlet 2 Exchanger outlet

3

Principle of operation

Heat transfer1.1 The rotor with its axial, smooth air channels serves as a storage mass, half of which is heated by the warm air stream and half of which is cooled by the cold air stream, in a counterflow arrangement. Consequently, the temperature of the storage mass varies depending on the axial co ordinate (rotor depth) and on the angle of rotation.The principle of operation is easy to understand by following the condition of an air channel during one revolution (see figure 3). From this process, the following can be seen:

The air temperature at the exchanger outlet is not uni- ●form; it depends on the angle of rotation.The heat recovery efficiency may be influenced by adjust- ●ing the speed of rotation.The heat recovery efficiency may also be influenced via ●the storage mass: wider or narrower air channels, differ-ent thickness of the storage material, other rotor depth. Pressure drop will also be affected.The specific heat output capacity depends on the tem- ●perature difference between the two air streams. Hence the rotary heat exchanger is suitable for heat as well as cool recovery, i.e. for winter and summer operation.

Conditions depending on the angle of rotationFig. 3:

Warm air entry

The wheel rotating at a speed of up to 20 rpm, the air channel in question has entered from the cold air into the warm air. The storage mass has been cooled down nearly to the cold air temperature. This applies particularly on the cold air inlet side (= warm air outlet).Now warm air flows through this channel, in counterflow as regards temperature, and is severely cooled in this process. In turn, the storage mass is heated. The local heat recovery efficiency, i.e. directly at the entry into warm air, is very high. Condensation can occur easily.

Mid warm air

This air channel has already passed half of its time in the warm air. The storage mass has become warmer due to the warm air flow; consequently the warm air is no longer cooled as severely as in the entry zone. The channel temperature is about the same on the inlet side and on the outlet side. Condensation occurs only if the humidity differential is great.

Warm air exit

The air channel is on the verge of leaving the warm air. On the inlet side it has nearly reached the tem perature of extract air. The heat transfer rate is now low.The duration of stay in the warm air as well as in the cold air, i.e. the speed of rotation, is decisive for the performance of the ro-tary heat exchanger. Also, the perform ance depends on the storage mass (thickness, geometry), the heat transfer and the air velocity.

Cold air exit

The air channel in question has gone through the cold air zone. The storage mass has been severely cooled; near the inlet the temperature has almost reached the temperature of cold air. After cross-over to the warm air side the cycle starts anew.

Mid cold air

Half of the dwell time in the cold air is over. The storage mass has become markedly colder. Temperatures at the inlet and at the outlet are about the same.

Cold air entry

After passover from the warm air side to the cold air side, cold air now flows through the channel (in counterflow as regards temperature). Due to the large temperature difference the heat transfer rate is very high, i.e. the cold air is strongly heated; in turn, the storage mass is severely cooled. Possible condensate on the exchanger surface is (partly) taken up by the heated cold air.

WARm AIR

COLD AIR

4

Principle of operation

moisture transfer1.2 Rotary heat exchangers can transfer moisture as well as heat. The decisive criterion for the transfer of moisture is the material or surface of the storage mass.

Three different designs are usual in the market:

Condensation wheel �The storage mass consists of smooth, untreated metal (mostly aluminium), transferring moisture only when conden-sation occurs on the warm air side and (part of) this is taken up by the cold air.The occurrence of condensation causes an increase in pres-sure drop. Condensation may be carried along with the air flow.

Hygroscopic wheel (enthalpy wheel) �The metallic storage mass has a capillary surface structure due to chemical treatment (pickling). Therefore (to a certain degree) moisture is transferred by sorption, i.e. without con-densation. Depending on the air conditions, conden sation may also occur.

Sorption wheel �Here the storage mass has a surface that transmits mois-ture by pure sorption, i.e. without condensation. Based on comprehensive measurements carried out in the HVAC test-ing centre of the Lucerne University of wheels from different manufacturers in the individual categories, characteristics can be given for the different designs. As a reference value for the moisture transfer rate the condensation potential is

Definition of the condensation potential κFig. 4:

Tem

pera

ture

Rel

. hum

idity

Water

Cold air entry (t21, x21)

Saturation humidity cold air

Warm air entry (t11, x11)

Condensation potential of warm air κ

Moi

stur

e re

cove

ry fi

gure

Ψ2

0

0.2

0.4

0.6

0.8

0.7

0.5

0.3

0.1

-4 -2 0 2 4 6 8 10

Sorption wheel

Hygroscopic wheel

Condensation wheel

Characteristic moisture recovery Fig. 5: figures of different wheel types depending on the condensation potential

Condensation potential κ [g/kg]

used; this is the difference between the warm air humidity and the saturation humidity of cold air (see figure 4).Please note the following:

The higher the condensation potential, the greater the ●expected amount of condensation on the warm air side.If the condensation potential is zero or negative, no ●condensation can occur. Hence the transfer of moisture is possible only by sorption.The given characteristics show typical values for a mass ●flow ratio of 1.0 and a pressure drop of about 130 Pa with an airway height of 1.9 mm.

5

Principle of operation

The scope of the reference value κ (= the condensation ●potential) is limited to the air conditions usual in ventila tion engineering. The heat recovery figure must be at least 70 %. The moisture recovery must not be limited by the saturation line (e.g. at very low outside tempera tures).

Based on the test results, the different wheel types may be characterised as follows:

Condensation wheel �The transfer of moisture is possible only if condensation oc-curs. With large temperature differences, moisture recovery figures up to 60 % may be achieved. Figure 6 shows that the moisture recovery figure of a condensation wheel is quite high over a broad temperature range and that moisture is transferred mainly when it is needed, i.e. during winter.

Hygroscopic wheel �Moisture is transferred by sorption as well as condensation, the contribution of sorption being very low. Therefore, the moisture transfer rate during so-called summer operation (κ < 0) is also low.(Moisture transfer by sorption depends on the chemical treat-ment and varies from one manufacturer to the next. At best, values of the sorption wheel can be achieved.)

Sorption wheel �The moisture recovery figure is almost independent of the condensation potential. The slight decline can be traced back to the temperature difference decreasing at the same time.

The following conclusions may be drawn:Condensation wheels are a good choice for heat and ●moisture recovery in air handling systems without me-chanical cooling, i.e. for winter operation. This becomes clear also from figure 7, showing the supply air humidity depending on the outside temperature for usual extract air conditions (22 °C / 50 % RH) (relating to average fresh air humidity according to VDI 2067). In comparison with a hygroscopic wheel, the supply air humidity is a little lower only in the temperature range between – 5 °C and + 10 °C.For cooling operation in summer, in other words when ●fresh air needs to be dried for mechanical cooling, sorp-tion wheels ought to be used.Hygroscopic wheels with low sorption rate are not neces- ●sary in winter operation and not efficient enough in sum-mer operation.

Moi

stur

e re

cove

ry

Fresh air temperature t21 [°C]

Moisture recovery figure of a condensation wheel depending on the Fig. 6: fresh air temperature t21 (for extract air at 22 °C / 50 %)

Hum

idity

[g/k

g]

Fresh air temperature t21 [°C]

Supply air (hygroscopic wheel)

Supply air (condensation wheel)

Fresh air

Supply air humidity depending on the fresh air temperature tFig. 7: 21 (for extract air at 22 °C / 50 %)

Leakage1.3 Components of air handling units, such as dampers, ducts or casings, are not normally 100 % leakproof. This is mainly be-cause it is not necessary to ensure the correct operation and it would be very expensive. In practical use, however, leak-age must not exceed technically justifiable limits. Therefore, test specifications and limits exist for cer tain components, such as dampers. For heat recovery units, there is no such data at the moment, however, actual values are known from tests.A distinction has to be made between leakage to outside (external leakage) and leakage between supply and extract air (internal leakage). While sealing to outside normally does not cause problems (it is above all a question of build qual-ity), the internal leakage mainly depends on the exchanger construction. Three aspects are important when talking about rotary heat exchangers:

6

Principle of operation

Carryover �To a minor degree, the two air flows mix due to the rotating storage mass. Depending on the air velocity and rotation speed, carryover amounts to about 2 % to 4 % of the air flow rate. Carryover of exhaust air to the fresh air side can be minimised by installing a purge sector. Yet a precondition for the correct function is a pressure gradient from the fresh air to the exhaust air (see also 10.9).

Peripheral seal �Sealing at the periphery is important for the internal leakage of the rotary heat exchanger. Hoval uses a costly but highly efficient slide seal: a plastic seal tape being pressed onto the storage mass by means of springs. This design keeps cross-contamination via the inside of the rotor casing to a minimum.

Transverse seal �A seal is also required between the warm air and the cold air. Hoval uses an adjustable threefold lip seal, ensuring a mini-mal air gap to the storage mass. This reduces direct carryo-ver from warm air to cold air (and vice versa) to a minimum.

Frost limit1.4 If the warm air stream is severely cooled down, it is not only possible for condensation to form but also to freeze. The cold air temperature at which freezing starts is called the 'frost limit'.

Condensation wheel: The condensation formed due to ●cooling of the warm air may freeze at low outside temper-atures. With equal mass flows on the warm air and cold air side, frost hazard exists if the mean air entry tempera-ture of the two air streams is lower than 5 °C.Sorption wheel: The vapour transfer by sorption usually ●prevents condensation; the frost hazard is low.

Heat recovery efficiency1.5 In principle, nearly any efficiency can be achieved if sized and designed to suit. The 'correct' efficiency is a subjective decision and depends on the economic calculation, i.e. on operating data such as energy prices, useful life, running times, temperatures, maintenance costs, interest rates, etc. It is important that the calculated optimum values for heat recovery efficiency and pressure drop are then put into prac-tice. Even small deviations (a few percent less efficiency, a few pascals more pressure drop) can cause substantially worse values for the present value and payback period.

Pressure drop1.6 Heat recovery units cause additional pressure drop on the extract and fresh air sides; incurring higher running costs. Under present conditions the economical values for

rotary heat exchangers range between 80 Pa and 130 Pa. However, to cut down costs, heat recovery units whose pressure drop exceeds these values are often installed. The profit ability of heat recovery is thereby jeopardised.

Pressure difference1.7 A distinction is made between the internal pressure dif-ference (between fresh air and exhaust air) and external pressure difference (between inside and outside of the exchanger).

External pressure difference: �This pressure difference has a major effect on the external leakage of the heat exchanger. However, when the exchang-er is properly and carefully installed in a ductwork system, its effect can be neglected.

Internal pressure difference: �Likewise, the internal pressure difference has a crucial influence on internal leakage between the two air streams. Although Hoval rotary heat exchangers are very tight in comparison with other constructions, the following should be considered when designing:

The pressure difference in the heat exchanger should be ●kept to a minimum.The pressure gradient and thus leakage should be from ●the fresh air to the exhaust air side.

The internal pressure difference also may cause a defor-mation of the casing; a pressure difference of more than 1500 Pa should therefore be avoided.

Notice The pressure difference depends on the position of the fans. Overpressure on one side and underpres-sure on the other side add up.

7

Performance control

Performance control2

Hoval rotary heat exchangers always operate as a tem pera-ture moderator between the two air streams. The direction of the heat transmission is of no consequence, i.e. depen ding on the temperature difference between extract air and fresh air, either heat or cool recovery takes place. Therefore per-formance control of the Hoval rotary heat exchanger is not necessary when the extract air temperature is identical with the desired room temperature. In this case, the fresh air is always either heated or cooled through the heat exchan ger in the direction of the set temperature.In many cases, however, heat gains are present in the ventilated space (people, machinery, lighting, solar, process plants), which increase the room temperature, so that the extract air temperature is higher than the set temperature. In this case, at full performance of the heat exchanger, check at which outside temperature heat-up begins, and if this cannot be tolerated, the performance of the heat exchanger must be controlled.

With the Hoval rotary heat exchanger the performance reduction for heat as well as moisture recovery is simply and economically accomplished by reducing the speed of rota-tion. All Hoval rotary exchangers can therefore be supplied with a controllable actuator.Performance control may also be accomplished by installing bypass dampers for one or both air streams. This possibil-ity – used mainly in process technology and with different air flow rates – is to be provided by the installer.

Rel

ativ

e he

at re

cove

ry0 5 10 15 20 25

0 %

20 %

40 %

60 %

80 %

100 %

Speed of rotation [rpm]

Dependency of heat recovery on the speed of rotationFig. 8:

Rel

ativ

e m

oist

ure

reco

very

0 5 10 15 20 250 %

20 %

40 %

60 %

80 %

100 %

Speed of rotation [rpm]

Dependency of moisture recovery on the speed of rotationFig. 9:

8

Construction

Construction3

A rotary heat exchanger consists of a rotor, a casing and an actuator.

Rotor3.1

Storage mass �A corrugated and a flat metal foil are each coiled to form the storage mass, creating triangular, axial air channels. The thickness of the material (usually aluminium) is 60 µ to 120 µ, depending on the application. Likewise, the surface treatment depends on the intended application; two different series are built:

Series A ●Condensation wheel, consisting of corrosion-resistant aluminium.Series S ●Sorption wheel, consisting of aluminium backing foil which is coated with a sorbent (e.g. silicagel) to accomplish vapour transfer without condensation.

The wheel is Fig. 10: assembled from alternate layers of flat and corrugated aluminium foil.

Production on Fig. 11: state-of-the-art machinery en-sures consistent, high quality.

Large wheels are Fig. 12: cut into several segments.

Construction �The depth of the rotor is 200 mm. The wheel is strengthened by means of double spokes, which are bolted (and welded) in the hub and welded in the rotor shell (see figure 13), en-suring a long life span.For reasons of rigidity and easy insertion, large rotors are divided into several segments. The rotor diameter can be selected as desired:

one-piece rotors in steps of 10 mm ●segmented rotors in steps of 50 mm ●

At the perimeter the rotor is enclosed by a welded aluminium shell, ensuring true running and allowing maximum use of the wheel face area.

Hub with inner bearing �The hub, whose size depends on the wheel diameter has an axle with two inner ball bearings. It is fitted in the cross-members of the casing. This bearing construction offers the following advantages:

The internal bearings are protected against dirt and re- ●quire little space.The axial restraint with Seeger circlips facilitate removal ●and replacement.Both bearings are installed in the hub, i.e. in the same ●part, ensuring exact alignment with each other (unlike exterior bearings). This does not affect the life span of the bearings.Due to the fixing of the inner ball bearings via the hub ●and Seeger circlips, the position of axle, hub and rotor is accurately fixed.The fixed axle links the two crossmembers of the casing, ●increasing its stability.

The rotor is stabilised by Fig. 13: means of welded double spokes.

Hub with long-lasting, Fig. 14: sealed-for-life inner bearing

9

Construction

Construction3

A rotary heat exchanger consists of a rotor, a casing and an actuator.

Rotor3.1

Storage mass �A corrugated and a flat metal foil are each coiled to form the storage mass, creating triangular, axial air channels. The thickness of the material (usually aluminium) is 60 µ to 120 µ, depending on the application. Likewise, the surface treatment depends on the intended application; two different series are built:

Series A ●Condensation wheel, consisting of corrosion-resistant aluminium.Series S ●Sorption wheel, consisting of aluminium backing foil which is coated with a sorbent (e.g. silicagel) to accomplish vapour transfer without condensation.

Rotor diameter (in mm)

Rot

or c

onst

ruct

ion

one-piece

segmented (4 segments)

segmented (8 segments)

Cas

ing

cons

truc

tion

Sheet steel casing, one-piece

Sheet steel casing, partitioned (only for 4-segment rotors)

Construction of sections

Req

uire

d dr

ivin

g to

rque

500 Nm

400 Nm

300 Nm

200 Nm

100 Nm

0 Nm

Designs and rotor dimensions (for standard casings)Table 1:

600

1500

2000

2550

2620

3000

3800

5000

10

Construction

3.2 Casing

Construction �The casing construction mainly depends on the rotor size. For wheels up to 2620 mm diameter, standardised self-sup-porting casings of Aluzinc sheet steel are employed. These are manufactured in two variants (see table 1):

Sheet steel casing, one-piece ●The rigid casing of Aluzinc sheet steel is composed of two face plates, the spacing adapters and two crossmembers supporting the rotor. For wheel sizes from a diameter of 1810 mm, the crossmembers have an additional support-ing strut in the middle.Sheet steel casing, partitioned ●The partitioned casing is composed of a base and hood. The base comprises the crossmembers with the rotor bearing. After insertion of the segmented wheel in the base, the hood is put over and fastened to the base.

Notice This partitioned design of the sheet steel casing does not allow for installation and assembly of segmented wheels from the front – and thus not inside a modular unit.

For diameters over 2620 mm a construction of extruded aluminium sections is used. The casing is characterised by high stability and dimensional flexibility. In addition, the face plates are easy to take off and refit, facilitating the assembly of segmented wheels. The height and width of this construc-tion of sections is limited to 4.5 m. Larger casings (galva-nised welded constructions) are built to special order.

Design �The casings are available in two different designs:

For installation in air handling units – design G ●The casing with the rotor is installed in an air handling unit. The casing sides are therefore open, enabling in-spection and maintenance works.For duct connection – design K ●Similar to design G, but the sides are closed. The side wall covering the actuator is designed as an inspection panel.

Sheet steel casings are built for one-piece rotors Fig. 15: up to a size of 2620 mm.

Special sizes �The outside casing dimensions may be adapted to exactly fit e.g. the inside cross-section of an air handling unit. In other words, the height and width of the casing can be se-lected as desired. (For maximum dimensions see section 7 'Dimensions and weights'). The hub may also be positioned off-centre.

Notice For special sizes the casing construction may deviate from the scheme shown in table 1.

Sealing �The plastic slide seal at the rotor periphery is pressed onto the rotor face and onto the frame by means of double springs. The transverse seal between the two air streams consist of an adjustable Aluzinc plate with a rubber lip seal.

Peripheral slide sealFig. 16: Transverse sealFig. 17:

11

Construction

Drive3.3 The wheel is driven by means of an electric motor and a drive belt. The motor is usually fixed on a hinged plate in the casing, on the left or on the right of the wheel.In many cases installers and AHU manufacturers install their own drive system, Hoval therefore offers this component as an option. There are two possibilities:

Constant drive �The motor is switched on and off via a simple switch or contact. Performance control (i.e. a variation of the heat or moisture recovery efficiency) is not possible.

Variable speed drive �The actuator is controlled by means of a control unit. As a rule, a frequency inverter is used for this. As ancillary functions motion detection (by means of an encoder) and so-called intermittent operation have become customary. In this operating mode the wheel is slightly moved at intervals to prevent clogging.The control unit and thus the rotor is usually controlled via room temperature, the cascade controller accessing the rotary heat exchanger as energy resource in heating as well as cooling operation.

Fig. 3–9: The Fig. 18: high-quality casings are built

on Hoval's state-of-the-art machinery.

12

Options

Options4

4.1 Drive motor AThe rotor is driven by means of a worm gear motor and a V-belt. The size of the motor relates to the wheel diameter.When connected to the mains directly the drive motor allows only on/off operation at constant speed. If the rotational speed and thus the performance of the rotary heat exchanger is to be controlled, a control unit (option R) is required.

Drive motorFig. 19:

Motor designation A 90 A 370 A 750 A 1500Power output kW 0.09 0.37 0.75 1.5Output shaft mm 20 x 50 20 x 50 25 x 50 25 x 50Current Y (mains operation) A 0.37 1.2 2.03 3.66Current Δ (with control unit) A 0.63 2.08 3.5 6.34cos φ 0.73 0.72 0.76 0.78Protection rating IP 54 IP 54 IP 54 IP 54Nominal motor speed n1 min-1 1280 1380 1370 1365Output speed n2 at 50 Hz min-1 85 138 137 195Nominal motor torque m1 Nm 0.67 2.6 5.2 10.5Output torque m2 Nm 6 16 31 44Wheel diameter mm up to 1200 up to 2700 up to 4000 up to 5000Control unit Type R54 / 370 R54 / 370 R54 / 750 R54 / 1500

Data sheet for drive motor ATable 2:

13

Options

Control unit R4.2

Construction �A frequency inverter is used as the control unit, allowing stepless speed variation of three-phase motors. Protective rating IP 54 is provided for installation in the air handling unit. The power section is pro tected against overvoltage, undervoltage and inadmis sible inverter temperature. The aluminium casing and the standard input and output filters increase the noise immuni ty. Fault messages can be read from a blinking LED.In principle, the control unit is factory-set and supplied ready for use. Individual parameter settings are possible using an optional operating unit (option B).

Function �The control unit can be used for condensation wheels and ●sorption wheels with different rotational speeds. It accepts all common control signals.Relating to the maximum frequency of the selected ●parameter set (condensation wheel or sorption wheel) translation of the set value into the rotating field frequency is alternatively linear or quadratic.When the input signal falls below the set threshold value ●the rotor stops. Then, after an adjustable lag time, inter-mittent operation starts: the wheel is turning at the ad-justed speed for a few seconds.For motion detection an encoder may be connected ●( option D).Readiness to operate and possible faults are signalled via ●a relay.

Design guidelines �The control unit is not built for outdoor use. ●The control unit is usually fitted to the side wall of the ●wheel casing.The installation position is strictly vertical. ●Provide sufficient ventilation for heat removal. ●

Installation �

Caution All transportation, installation, commissioning and maintenance works are to be carried out by qualified staff (observe IEC 364 or VENELEC HD 384 or DIN VDE 0100 and IEC report 664 or DIN VDE 0110 as well as national accident prevention regulations or VGB 4).

Qualified staff under these fundamental safety instruc tions are persons familiar with setting up, installing, commis-sioning and operating the product, having the necessary

qualifications for their respective tasks (stipulated in IEC 364 or DIN VDE 0105).

Commissioning �Before starting up the control unit make sure that the ●rotary heat exchanger works properly.The direction of rotation may be altered by changing over ●the motor phases.During failure-free operation a green LED lights up. ●Possible failure causes are shown on the control unit. ●

Control unit R54Fig. 20:

14

Options

4.3 Operating unit BThe operating unit allows for individual setting of the control unit. Parametrisation is easy and quick thanks to the LCD graphic display, the clear menu structure and parameter plain text display.

Motion detection D4.4 The motion of the wheel may be monitored by means of an encoder on the wheel periphery. This way a possible stand-still, e.g. due to a torn V-belt, can quickly be detected and remedied.

Purge sector S4.5 The purge sector minimises carryover from the extract air to the supply air stream (see also 1.3 and 10.9).

Notice The purge sector is only available from a wheel diameter of 1000 mm.

Inspection port I4.6 Inspection ports allow for visual checks of the motor and V-belt. They are particularly recommended in applications where inspections are not possible from the side. The cas-ings are available with either one or two inspection ports.

Notice It is not always possible to install inspection ports in casings with small dimensions. If this is the case, it is shown in the selection program Hoval CARS. For detailed information please seek Hoval advice.

R54/370 (Type: F-D 370-WT VECTOR IP54)R54/750 (Type: F-D 750-WT VECTOR IP54)

7

1

2

3

4

5

6

8

9

10

11

12

13

14

15

16

17

18

19

B1

10k

+10 V Reference voltageAnalog setpoint inputGND (analog)Analog output+15 V (max. 100 mA)Start clockwise rotationExternal sensorPriority speed of rotationParameter set switchingEnableGND (digital)Relay output 1 (make contact)Relay output 1 (change-over contact)Relay output 1 (break contact)PTC motor temperature monitoringPTC motor temperature monitoring

Relay output 2 (make contact)Relay output 2 (change-over contact)Relay output 2 (break contact)

Terminals 1, 2, 3 Connection of the control signalTerminals 5, 7, 11 Connection of the encoder for motion detectionTerminal 6 Rotor start (terminal 10 must be live)Terminal 9 not live Operating mode sorption wheelTerminal 9 live Operating mode condensation wheelTerminal 10 Reset function by short-time voltage interruption,

acknowledgment of faultsTerminals 15, 16 Connection of thermal contacts of the motorTerminals 17, 18, 19 Volt-free output for output of faults via relay

Terminal connection diagram of control inputs for the control units R54/370 and R54/ 750Table 3:

R54/370 R54/750 R54/1500Output to motor Max. motor power kW 0.37 0.75 1.50

Nominal output current A 2.2 4.0 7.0Max. output voltage V 3 x 230 3 x 230 3 x 230Output frequency Hz 0..500 0..500 0..250

Input from mains Nominal voltage V 230 230 230Supply frequency Hz 50/60 50/60 50/60Fuse protection A T 6 8 12

General data Protection rating IP 54 IP 54 IP 54Ambient temperature °C 0..40 0..40 0..40Air humidity % 20..90 20..90 20..90Power loss W 35 45 100

Dimensions Height x width x depth mm 282 x 112 x 70 282 x 112 x 70 353 x 180 x 77

Technical data of control unitsTable 4:

Notice Terminal con-nection diagram for R54/1500 available on demand.

15

Options

4.3 Operating unit BThe operating unit allows for individual setting of the control unit. Parametrisation is easy and quick thanks to the LCD graphic display, the clear menu structure and parameter plain text display.

Motion detection D4.4 The motion of the wheel may be monitored by means of an encoder on the wheel periphery. This way a possible stand-still, e.g. due to a torn V-belt, can quickly be detected and remedied.

Purge sector S4.5 The purge sector minimises carryover from the extract air to the supply air stream (see also 1.3 and 10.9).

Notice The purge sector is only available from a wheel diameter of 1000 mm.

Inspection port I4.6 Inspection ports allow for visual checks of the motor and V-belt. They are particularly recommended in applications where inspections are not possible from the side. The cas-ings are available with either one or two inspection ports.

Notice It is not always possible to install inspection ports in casings with small dimensions. If this is the case, it is shown in the selection program Hoval CARS. For detailed information please seek Hoval advice.

Operating unit BFig. 21:

Purge sector SFig. 22:

Carryover of extract Fig. 23: air to the supply air can be minimised by installing a purge sector.

Inspection port IFig. 24:

Fresh air

Exhaust air

16

Unit type reference

Unit type reference5

ArrangementAir flow case A, B, C or D (cf. page 28)(The arrangement is not relevant for the design and hence not part of the type designation in the selection program.)

Installation positionV = verticalH = horizontal(The installation position is not relevant for the design and hence not part of the type designation in the selection program.)

Wheel typeA = Condensation wheel of aluminiumS = Sorption wheel with sorbent coating

Rotor construction1 = one-piece wheel, normally delivered in assembled

form (installed in the casing)4 = 4-segment wheel, normally with construction of

sections so that the 4 segments can be removed and replaced anytime. Under certain conditions a sheet steel casing is available as well.

8 = 8-segment wheel, always with construction of sections

Wheel diameter (in mm)Can be selected as desired in steps of 10 mm (one-piece wheels) or 50 mm (4- or 8-segment wheels)

Airway height (in mm)1.6 mm1.9 mm2.9 mm

Example of type designation

AV-A1-1500/1.9 - GM -A1580xB1580 -A1,1IV,…

17

Unit type reference

Casing designG = Casing for installation in AHU (open sides)K = Casing for duct connection (closed sides)

DeliveryM = The wheel is installed in the casing (standard for one-piece wheels, optional

for 4- and 8-segment wheels with construction of sections).G = The wheel segments and the casing are delivered separate, for assembly

on site (for 4- or 8-segment wheels with construction of sections).B = The 4 wheel segments and the casing are delivered separate, for assembly

on site (only for 4-segment wheels with sheet steel casing).

Notice Insertion of the wheel segments is only possible while the upper half of the casing is off. Therefore the installation e.g. into a closed air handling unit is not possible.

Casing size (in mm)Dimension A x dimension B, can be selected as desired

OptionsA = Drive motor

1..4 indicates the position (= not part of the type designation in the selection program)R54 = Control unitB = Operating unitD = Motion detectionS = Purge sectorI = Inspection ports, installed in the drive corner

Indicate number: 1I or 2I V (= front) or H (= rear) indicates the position if only 1 inspection port is selected (cf. page 28, not part of the type designation in the selection program)

Example of type designation

AV-A1-1500/1.9 - GM -A1580xB1580 -A1,1IV,…

18

Design calculation

Design calculation6

Design data6.1 When designing, correct data is essential to achieve the de-sired values. This is often particularly difficult in air handling installations because the specific density and specific heat are dependent on temperature. Also the water vapour con-tained in the air is very important for the design. For an exact calculation of a heat exchanger the air conditions at entry to the exchanger are required (see also section 10.1).

Warm air Air flow rate at exchanger entry V11 m³/sRel. humidity at exchanger entry RH11 %Temperature at exchanger entry t11 °CMax. pressure drop Δp1 Pa

Cold air Air flow rate at exchanger entry V21 m³/sRel. humidity at exchanger entry RH21 %Temperature at exchanger entry t21 °CMax. pressure drop Δp2 Pa

Design dataTable 5:

For an economic calculation the following data is required:Desired temperature ●Operation time ●Location (region or climatic zone) ●Energy costs (with increase rate) ●Cost of electricity ●Additional costs (installation and extra costs ●minus capital savings and subsidies)Interest rate ●

Selection program Hoval CAPS6.2 The design of Hoval rotary heat exchangers is easy and quick with the selection program Hoval CARS (= Computer Aided Rotary Heat Exchanger Selection). It runs under Microsoft® Windows and offers the following:

Reliable design data thanks to Eurovent-certified data ●Exact calculation of a specific Hoval rotary heat ●exchangerCalculation of all appropriate rotary heat exchangers for a ●specific projectPrice calculation ●

Notice The selection program Hoval CAPS is available for download on our homepage (www.hoval.com).

The selection program Hoval CARS is also available as Windows DLL file for implementation into other calculation programs (on request).

Performance chart6.3 Calculation of the heat recovery efficiency and pressure drop with the performance chart is an approximate method, whose accuracy in most cases is sufficient for temperatures between –15°C and +25°C (see figure 26, 27).

Tested data6.4 Especially for rotary heat exchangers, where the processes of heat and material transmission are quite complex, it is es-sential that theoretically found values are verified by inde-pendent testing. Therefore, Hoval has had tested all relevant data

heat recovery efficiency ●moisture recovery efficiency ●pressure drop ●

at different mass flows, mass flow ratios and rotation speeds in the HVAC testing centre of the Lucerne University. Tests have been carried out under EN 308. All given data are based on these test results – to safeguard designers, install-ers and operators.

Sorptionsrotor

Winter Sommer Aussenluft Abluft Abluft Aussenluft 2 1 1 2 Leistungen Rückwärmzahl Φ 79,6 79,2 79,6 79,2 % Rückfeuchtzahl Ψ 82,1 82,1 79,7 79,7 % Druckverlust Δp 73 73 73 73 Pa Volumenstrom V 9000 9000 9000 9000 m3/h - bei Dichte ρ 1,2 1,2 1,2 1,2 kg/m3 Massenstrom m 10775 10775 10775 10775 kg/h Geschwindigkeit w 1,7 1,7 1,7 1,7 m/s Leistung Q 113 -113 49,7 -49,7 kW Eintritt Temperatur t -10 22 25 30 °C relative Feuchte rF 90 45 50 60 % absolute Feuchte x 1,6 7,4 9,9 16 g/kg Austritt Temperatur t 15,5 -3,4 29 26 °C relative Feuchte rF 58,1 88,8 58,5 52,6 % absolute Feuchte x 6,4 2,6 14,8 11,1 g/kg Neben unseren allgemeinen Lieferbedingungen gelten folgende Konditionen: • Zahlung - • Lieferung - • Verpackung - • Bindung - • Liefertermin -

Hoval®CARS, 2008000013006-10000-00001-00000-00001 DB11032009135144.doc

Firma -Projekt - Datum -

Typ

S4 200/1,9-GG 220X220-A,R54,D,2I

Preis 0 CHF Rotorausführung S 4 vierteiliger Rotor Rotordurchmesser 2000 mm G Gehäuse für Geräteeinbau Lagenhöhe 1,9 mm G Lieferung Profilkonstruktion geteilt Gehäusemass A 2200 mm Gehäusemass B 2200 mm X Antrieb A/370 Gehäusetiefe T 430 mm Regelgerät R20 Luftdruck 1013 hPa X Regelgerät R54/370 Folienstärke 0,06 mm Bedieneinheit B Rotordrehzahl 20 1/min X Drehzahlüberwachung D Gehäusekonstruktion Profilkonstruktion Spülzone S Gewicht ca. 334 kg 2 Inspektionsdeckel 1I,2I

The design of Hoval Fig. 25: rotary heat exchangers is easy and quick with the selection program Hoval CARS.

19

Design calculation

Performance chart6.3 Calculation of the heat recovery efficiency and pressure drop with the performance chart is an approximate method, whose accuracy in most cases is sufficient for temperatures between –15°C and +25°C (see figure 26, 27).

Tested data6.4 Especially for rotary heat exchangers, where the processes of heat and material transmission are quite complex, it is es-sential that theoretically found values are verified by inde-pendent testing. Therefore, Hoval has had tested all relevant data

heat recovery efficiency ●moisture recovery efficiency ●pressure drop ●

at different mass flows, mass flow ratios and rotation speeds in the HVAC testing centre of the Lucerne University. Tests have been carried out under EN 308. All given data are based on these test results – to safeguard designers, install-ers and operators.

Pre

ssur

e dr

op Δ

p [P

a]

50

60

70

80

90

100

110

120

130

140

150

160

170

180

19062

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

100 1'000 10'000 100'000 1'000'000

0.50

m

0.60

m

0.70

m

0.80

m

0.95

m

1.10

m

1.30

m

1.50

m

1.70

m

2.00

m

2.30

m

2.60

m

2.90

m3.20

m

3.60

m

4.00

m

4.50

m

5.00

m

7000

96 73,4

2,0

2,2

2,4

2,6

2,8

3,0

3,2

3,4

3,6

3,8

4,0

4,2

4,4

4,6

5,2

4,8

5,4

5,0

Hea

t rec

over

y fig

ure

Φ2

[%]

Air flow rate V [m³/h]

Relates to: Air density 1.2 kg/m³ Mass flow ratio 1.0 Airway height 1.9 mm

Performance chart for determination of the pressure drop and heat recovery figure for different wheel sizesFig. 26:

Moi

stur

e re

cove

ry fi

gure

Ψ2

-4-6 -2 0 2 4 6 8 100.0

0.2

0.4

0.6

0.7

0.5

0.3

0.1

0.8Sorption wheel

Condensation wheel

Condensation potential κ [g/kg]

Moisture transmission of different Fig. 27: wheel types

Relates to: Pressure drop 100 Pa Airway height 1.9 mm

Face velocity w [m/s]

20

Dimensions and weights

Dimensions and weights7

The size of the casing relates to the wheel diameter. Please find below the dimensions and weights of some selected sizes. The outside dimensions may be individually speci-fied; the heights and widths given in the table are minimum dimensions for the respective wheel size.

Notice For wheel diameters up to 1550 mm the drive motor does not fit into the given minimum casing size. For detailed information please seek Hoval advice.

The weights refer to rotary heat exchangers with casing (design G), airway height 1.9 mm, without drive, without packing.

A (max. 2850)

B (m

ax. 2

700)

320

75

40

75

1) Additional supporting strut for rotor diameters from 1810 mm

Dimensions for one-piece sheet steel casings (design G)Fig. 28:

Rotor ∅[mm]

minimum casing size [mm] Weight[kg]

A = B A = B A x B | B x A 600 680 910 680 x 1140 53 700 780 980 780 x 1180 59 800 880 1055 880 x 1225 66 900 980 1125 980 x 1265 741000 1080 1195 1080 x 1305 821100 1180 1265 1180 x 1350 921200 1280 1335 1280 x 1390 1011300 1380 1460 1380 x 1535 1201400 1480 1530 1480 x 1580 1391500 1580 1600 1580 x 1620 1531600 1680

The drive motor A always fits into the casing.

1671700 1780 1821800 1880 1981900 1980 2142000 2080 2312100 2180 2492200 2280 2682300 2380 2882400 2480 3082500 2580 3412620 2700 367Minimum size without drive motor A

Minimum square size with drive motor A

Minimum rectangular size with drive motor A

Minimum sizes and weights for one-piece rotors Table 6:

1)

21

Dimensions and weights

A (max. 2850)

B (m

ax. 2

700)

320

75

40

75

Dimensions for partitioned sheet steel casing (design G)Fig. 29:

Rotor ∅[mm]

minimum casing size [mm]

Weight[kg]

A = B1500 1650 2191600 1750 2381700 1850 2571800 1950 2771900 2050 2982000 2150 3202100 2250 3422200 2350 3662300 2450 3902400 2550 4142500 2650 4522550 2700 465

Minimum sizes and weights for 4-segment rotors with partitioned Table 7: sheet steel casing

A (max. 4500)

B (m

ax. 4

500)

430

70

70

70

Dimensions for construction of sections (design G)Fig. 30:

Rotor ∅[mm]

minimum casing size [mm]

Weight [kg]

A = B 4-segment 8-segment1500 1700 229 –1600 1800 248 –1800 2000 288 –2000 2200 331 3822200 2400 377 4332400 2600 426 4872600 2800 490 5562800 3000 550 6213000 3200 608 6843200 3400 – 7503400 3600 – 8193600 3800 – 8903800 4000 – 965

Minimum sizes and weights for segmented rotors with construction Table 8: of sections

22

Transport and installation

Transport and installation8

The following should be checked before installation:Has the rotary heat exchanger been damaged during ●transport? (visual check of casing and rotor)Has the correct type been delivered (design, series, size, ●options)?How is the exchanger to be positioned (purge sector)? ●(→ note the label!)

Transportation8.1 The rotor should be vertical during transport. ●The rotary heat exchanger should be lifted by the cross­ ●members of the casing. To avoid damage, the lifting slings must be vertical.In general: Do not suspend the exchanger from one point ●but always under a crane beam (see figure 31).

Mechanical installation8.2 The casing design K (for duct connection) may be bolted ●or riveted at the face plate up to 4 cm from the outer frame.

Attention Please note: The casing cannot take up any extra load (e.g. ducts).

For installation of the rotary heat exchanger in an air ●handling unit the casing dimensions should be reason ably adapted to the unit size.If required, baffle plates may be installed to adapt the cas­ ●ing to the unit's cross section.

Attention Take care that the wheel is not damaged or blocked and that sealings remain intact.

If the exchanger is to be installed in horizontal or inclined ●position, vertical forces must be supported at the bearing.After installation, check if the rotor runs smoothly. ●Readjust sealing as necessary.

Condensate drain connection8.3 If condensation is expected, make sure that this can drain away freely. We recommend condensate drip trays on both sides, i.e. for both air streams. Correspondingly sized con­densate drains should be installed.

Fitting of sensors8.4 If for example temperature sensors are required in the cas­ing make sure that the wheel rotation is not obstructed by their installation.

Lifting the exchangerFig. 31:

Bolting areaFig. 32:

Matched casing dimensionsFig. 33:

23

Commissioning and maintenance

Electrical connection8.5

Constant drive �The actuator is to be electrically connected by the installer (star connection). The direction of rotation may be altered by changing over the phases.

Variable speed drive �Control unit fitted in or at the casing: ●Wiring from the actuator to the control unit is factory-fitted. Connection to the control unit is to be carried out by the installer.External control unit: ●Wiring from the actuator to the control unit as well as connection of the control unit are to be effected by the installer.

Assembly of segmented rotary heat exchangers8.6 To ensure correct assembly, supervision by a Hoval expert or by an authorised specialist is recommended.

Horizontal installation8.7 If the rotor is to be installed in horizontal position, a special design must be ordered. Consultation with the manufac-turer is recommended. The bearing is to be supported at installation.

Commissioning and maintenance9

Commissioning9.1 Prior to start-up make sure that the air streams can flow ●freely through the exchanger.Check if the exchanger has been properly installed and ●make sure that the application limits (temperature, pres-sure difference, etc.) cannot be exceeded.Check if the wheel rotates in the correct direction and if ●the control unit works correctly (with optional functions, where appropriate).Check tension of the drive belt and fixing of the actuator. ●Visually check the wheel sealings. In case of readjust- ●ments, make sure the wheel can rotate easily and is not blocked. The required driving torques indicated in table 1 must not be exceeded.

maintenance9.2 Only periodic visual checks are necessary. After initial 3-monthly inspection intervals, checks may be carried out every 12 months. Check the following:

Tension of drive belt ●Sealing of drive motor ●State of the bearings (assess via bearing noise) ●Function of slide seal ●Function of transverse seal ●Casing condition ●Wheel condition ●

Based on long experience, clogging of heat exchangers installed in air handling equipment is not expected. However, should dirt enter the exchanger when used for special ap-plications, the exchanger may be cleaned as follows:

Remove dust and fibres with a soft brush or with a vacu- ●um cleaner. Take care when cleaning with com pressed air that the wheel is not damaged. Keep at a distance!Oils, solutions, etc. can be removed with hot water ●(max. 70 °C) or grease solvents, by washing or immers-ing. Cleaning with high-pressure devices is possible if: – a flat nozzle 40° is used (type WEG40/04) – the max. water pressure is 100 bar

Attention When cleaning take care that the exchanger is not damaged, neither mechanically nor chemically: → Choose harmless cleansing agents. → Clean carefully. The material thickness is less

than 0.1 mm!

24

Design considerations

Design considerations10

Data collection10.1 The data listed in section 6 is necessary when designing and planning. For exact design the following errors should be avoided when collecting the data:

Volume flow is not equal to mass flow. For an accurate ●design the mass flows of fresh and extract air should be known.For winter operation the moisture in the air is often esti- ●mated too high. (Where does the moisture come from?)Are the temperatures (fresh air, extract air) really as ●stated in practice (or are they wishful thinking)?

Rules and guidelines10.2 Ascertain before designing which rules and guidelines apply. For instance, for some applications (e.g. hospitals) some heat recovery systems are not suitable or can only be al-lowed after appropriate proving.

Positioning of units10.3 Where should the heat recovery unit be positioned? ●Which is the optimum air path? ●Which dimensions are allowed? ●Should the rotor be installed horizontally? ●

Wheel type10.4 Depending on the application, decide which wheel type (condensation wheel, sorption wheel) should be used. We recommend the following:

For air handling installations without mechanical cool- ●ing and without humidity control a condensation wheel is sufficient.For air handling installations with mechanical cooling a ●sorption wheel is recommended for drying humid fresh air in cooling operation. As a rule, the same applies for installations with humidity control (depending on internal moisture gains).

Cost-effective design10.5 Select the most economical type regarding efficiency and pressure drop. The following rules apply:

long periods of operation (e.g. 3 operating shifts) → high ●efficiency, low pressure drophigh dirt hazard → large airway height ●

The optimum rotary heat exchanger selection can only be based on an economic efficiency calculation.

Performance control10.6 Check which internal heat sources are available in the ventilated room. If the extract air temperature is expected to

be clearly higher than the desired temperature, a perform-ance control (speed control) should be considered (see also section 2).

Bypass10.7 With different air flow rates during recirculation or mixed air operation, it may be useful to install a bypass in parallel with the rotor. The bypass should be sized in a way to cause equal pressure drop through the bypass as through the wheel.

Fresh airExhaust airFresh air bypassExhaust air bypassRecirculation

Bypass arrangementFig. 34:

Frost limit10.8 If condensation can form and could freeze, provide adequate precautionary measures (pre-heating, bypass, etc.). For more detailed information please seek Hoval advice.Frost hazard exists if:

t11 + t21 tm =   ≤ 5° C 2

Also consider that, at low supply air temperatures, conden-sation can form and even freeze on the outside of air ducts.

25

Design considerations

Use and sizing of the purge sector10.9

Fresh air Supply air Both fans on suction sideTo ensure the correct func-tion of the purge sector, a pressure gradient from the fresh air to the exhaust air stream of at least 200 Pa is needed.

Exhaust air Extract air

Fresh air Supply air Exhaust fan on suction side, fresh air fan on pres-sure sideTo keep the flowrate through the purge sector low, avoid major pressure gradients (> 600 Pa). It may be advis-able to use a small purge sector (2 x 3°).Exhaust air Extract air

Fresh air Supply air Both fans on pressure sideTo ensure the correct func-tion of the purge sector, a pressure gradient from the fresh air to the exhaust air stream of at least 200 Pa is needed.

Exhaust air Extract air

Fresh air Supply air Extract fan on pressure side, supply fan on suction sideThis arrangement is not rec-ommended. Extract air may be carried over to the supply air stream. The purge sector is useless.

Exhaust air Extract air

The size of the purge sector depends on the pressure differ-ence between fresh air and exhaust air. (If this is unknown a standard purge sector of 5° is installed.)

up to 200 Pa Purge sector ineffective200 – 600 Pa Standard purge sector (2 x 5°)

recommended600 – 900 Pa Small purge sector (2 x 3°) recommended

over 900 Pa Purge sector useless

Size recommendations for purge sectorsTable 9:

Since the purge sector virtually bypasses the fresh air via the rotor to the exhaust air, it also changes temperature of the storage mass. Test results show that the heat recovery efficiency is lowered by about 1 %.

Internal leakage10.10 The internal leakage from the fresh air to the exhaust air side depends on the corresponding pressure difference:

Δp = p21 − p12

It is composed of the sealing leakage and the purge flow rate. For an approximate calculation please contact the Hoval technical department.

Pressure difference10.11 To keep internal leakage within acceptable limits, the pres-sure difference between fresh air and exhaust air should not exceed 1500 Pa. The maximum pressure difference allowed is 2000 Pa.

Cross-contamination10.12 In principle, cross-contamination between the two air streams is inevitable when using rotary heat exchangers. Therefore, unless special precautionary measures are taken, adhere to the VDI 6022 standard: 'Regenerators using ro-tors are only to be used if, from the point of view of hygiene, it would also be possible to use recirculation.' Cross-contamination is due to the following:

Carryover (see also 1.3 and 10.9) ●A certain amount of air (depending on rotation speed, air velocity and rotor construction) is carried over from one air stream to the other inside the rotor.Leakage (see also 1.3) ●Depending on the pressure gradient and the quality of seals, there is leakage through the peripheral and trans-verse seals.Contamination ●Since the storage mass passes alternately through the two air streams, they can influence each other. This way, minute particles and thus odours (e.g. cigarette smoke) can be transmitted.Transmission of substances ●Rotary heat exchangers also transmit gaseous sub-stances. The quantity depends on the wheel type and on the sub stance itself. Unfortunately, only a small amount of measure ment data is available; on the other hand it is known from practical experience that normally this does not cause prob lems in air conditioning systems.

In rare cases odorous substances can 'accumulate' inside the wheel and be emitted again under extreme fresh air con-ditions (very high relative humidity). This may cause odour problems. However, in most cases problems can be avoided

26

Design considerations

by specially adjusting the cleaning operation or by setting a minimum rotation speed.

Supply air humidification10.13 The humidifier downstream of the rotor is to be sized in a way to achieve the desired value even at minimum fresh air humidity. Since the rotor speed is usually controlled depending on the supply air temperature the corresponding moisture content is to be taken into account when sizing the humidifier.

Corrosion10.14 Hoval rotary heat exchangers series A (aluminium) have proved satisfactory for installation in air handling equipment. If a corrosion hazard exists, such as e.g. in kitchens or in certain industrial applications, coated aluminium is usually adequate. The Hoval technical department will advise what is suitable for specific applications.

Application limits10.15 Prior to selecting a rotary heat exchanger, check if any ap-plication limits are exceeded:

Temperature -40…70 °CPressure difference max. 2000 PaPressure diff. to outside max. 2000 PaPressure drop 80…100 Pa (recommendation)

Application limitsTable 10:

Clogging10.16 In 'normal' air handling equipment the air streams are mostly cleaned with coarse dust filters. Therefore there is no dirt hazard for the rotary heat exchanger. Yet if clogging is ex-pected in special applications consider the following:

Install the exchanger in such a way that it is easy to clean ●without removal orfit inspection ports before and after the rotary heat ●exchanger.If possible, filter the air streams so that dirt built-up is ●minimised or cleaning intervals are longer.

It was found in practice that dirt built-up is far less than ex-pected. The Hoval technical department will advise.

Condensation in the warm air stream10.17 If more water condenses from the warm air than the (heated) cold air can take up, condensate is formed. Since, due to thermodynamics this occurs mainly in the first third of the warm wheel side, part of it is carried along by the warm air flow. This is to be considered concerning the component next in line. In general, condensate drip trays should be

installed on the warm air as well as on the cold air side. In addition, check the following and arrange for appropriate measures:

How is the condensate drained away? ●Does frost hazard exist (see sections 1.4 and 10.8)? ●

Exchanger selection10.18 With the acquired data and known conditions the rotary heat exchanger can now be selected. This can be done with the computer program Hoval CARS. It calculates suitable selec-tions, complete with technical data and prices.

Technical data10.19 The following data defines the selected rotary heat exchang-er and its performance.

TypeWeight kgHeight x width x length mmRotor diameter mm

Warm air:Air flow rate at exchanger entry V11 m3/sTemperature at exchanger entry t11 °CRel. humidity at exchanger entry rF11 %Rel. humidity at exchanger exit rF12 %Temperature at exchanger exit t12 °CPressure drop (with condensation) ∆p1 Pa

Cold air:Air flow rate at exchanger entry V21 m3/sTemperature at exchanger entry t21 °CRel. humidity at exchanger entry rF21 %Rel. humidity at exchanger exit rF22 %Temperature at exchanger exit t22 °CPressure drop ∆p2 PaMass flow ratio m2/m1

Notice For the exact specification of a wheel state data in winter operation as well as summer operation.

27

Specification texts

Specification texts11

Condensation wheel11.1 Rotary heat exchanger for heat transfer consisting of rotor and casing:

Rotor �The storage mass consists of coiled layers of corrugated and smooth, corrosion-resistant aluminium foils. Thus small, axially arranged, smooth air channels for laminar flow are formed. At the periphery the storage mass is enclosed within the rotor shell; in the centre there is the hub with sealed-for-life, maintenance-free ball bearings and the axle. The wheel is stabilised by spokes between the rotor shell and hub.The storage mass consists of pure aluminium.

Casing �The casing is suitable for installation in air handling units or for duct connection. There is a high-quality peripheral slide seal on both sides, which by means of double-acting springs re duces internal leakage to a minimum. As transverse seal a lip seal is used. The drive motor for the wheel may also be fitted in the casing.

Self-supporting construction of Aluzinc sheet steel ●Construction of extruded aluminium sections with face ●plates of Aluzinc sheet steel

Options �Drive motor A: three-phase drive motor with belt pulley ●and V-belt.Control unit R54: for continuous speed control; protection ●rating IP 54. The software includes motion detection and intermittent operation for cleaning.Operating unit B: allows for programme alterations and ●manual operation (to be plugged into the R54 control unit).Motion detection D: by means of an inductive sensor and ●a corresponding transmitter on the wheel periphery.Purge sector: prevents carryover from the extract air to ●the supply air if there is a pressure gradient between sup-ply air inlet and exhaust air outlet.Inspection ports: allow for visual checks of the motor and ●V-belt.

Sorption wheel11.2 Rotary heat exchanger for heat and moisture transfer con-sisting of rotor and casing:

Rotor �The storage mass consists of coiled layers of corrugated and smooth, corrosion-resistant aluminium foils with a silicagel coating for the transfer of moisture. Thus small, axially ar-ranged, smooth air channels for laminar flow are formed. At the periphery the storage mass is enclosed within the rotor shell; in the centre there is the hub with sealed-for-life, maintenance-free ball bearings and the axle. The wheel is stabilised by spokes between the rotor shell and hub.The storage mass consists of corrosion-resistant aluminium foil which is coated with a high-efficient sorbent for the trans-fer of moisture.

Casing �The casing is suitable for installation in air handling units or for duct connection. There is a high-quality peripheral slide seal on both sides, which by means of double-acting springs re duces internal leakage to a minimum. As transverse seal a lip seal is used. The drive motor for the wheel may also be fitted in the casing.

Self-supporting construction of Aluzinc sheet steel ●Construction of extruded aluminium sections with face ●plates of Aluzinc sheet steel

Options �Drive motor A: three-phase drive motor with belt pulley ●and V-belt.Control unit R54: for continuous speed control; protection ●rating IP 54. The software includes motion detection and intermittent operation for cleaning.Operating unit B: allows for programme alterations and ●manual operation (to be plugged into the R54 control unit).Motion detection D: by means of an inductive sensor and ●a corresponding transmitter on the wheel periphery.Purge sector: prevents carryover from the extract air to ●the supply air if there is a pressure gradient between sup-ply air inlet and exhaust air outlet.Inspection ports: allow for visual checks of the motor and ●V-belt.

28

Supplementary Sheet for OrderingRotary Heat Exchangers

Company:

Contact:

Client order No.:

Rotor type:

Date:

Case A

Extract air

Supply air

Case B

Supply air

Extract air

Air flow above and belowView on extract air inlet

Case C

Supply air

Extract air

Case D

Supply air

Extract air

Air flows side by sideView on extract air inlet

Arrangement  Case A  Case B  Case C  Case D

Drive / mounting plate  Pos. 1  Pos. 2  Pos. 3  Pos. 4

Dimensions Dimension A = ______ mm Dimension B = ______ mm

Inspection ports  None  1 pc front side  1 pc rear side

Purge sector  No  Yes (clockwise rotation)

Installation position  Vertical  Horizontal  Inclined

Remarks

________________________

________________________

________________________

________________________

The Hoval group with production facilities and sales offices in more than 50 countries worldwide has the above guiding principle. The company, established in 1945, is a pioneer in heating technology. Today Hoval develops and manufactures innovative solutions that maximise energy efficiency and thus help protect the environment in the following product lines:

Hoval Heating Technology.From a comprehensive range Hoval offers innovative system solutions for a variety of energy sources (oil, gas, wood, pellets and solar) as well as heat pumps. The range of performance extends from a small apartment to a tower block.

Hoval Residential Ventilation.A better atmosphere and heat energy efficiency in your own home: With the HomeVent® Hoval sets the standards in air quality for single family houses and apartments.

Hoval Indoor Climate Systems.Supply fresh air, remove extract air, heat and cool, filter and distribute air, make use of waste heat or recover cooling energy: Whatever the task may be – Hoval systems can provide a tailor-made answer with minimal design and installation outlay.

Hoval Heat Recovery.Efficient energy use through heat recovery: Hoval offers two different solutions: plate heat exchangers as a recuperative system and rotary heat exchangers as a regenerative system.

Conservation of EnergyProtection of the Environment

Hovalwerk AGAustrasse 70, 9490 Vaduz, Liechtensteintel + 423 399 24 00, fax + 423 399 27 31info.lufttechnik@ hoval.com, www.hoval.com

Conservation of Energy – Protection of the Environment

Art.

Nr.

4 20

8 53

4 –

04 / 2

009