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Manual for the program COIL Tube Coil Heat Exchanger and Coaxial Tube Heat Exchangers Lauterbach Verfahrenstechnik GmbH 1 / 2011

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Page 1: COIL-E

Manual for the program

COIL

Tube Coil Heat Exchanger and Coaxial Tube Heat Exchangers

Lauterbach Verfahrenstechnik GmbH

1 / 2011

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COIL Manual Contents i

Contents

Program description 3 Program features ...............................................................................................................................................3

Design of Tube Coil Heat Exchangers..................................................................................................3 Design of Coaxial Tube Heat Exchangers (coiled double-pipe) ...........................................................3

Program structure 4 Structure of the program....................................................................................................................................4

The modules of COIL............................................................................................................................4

Operation 5 Starting COIL .....................................................................................................................................................5 Menu ’Path’........................................................................................................................................................5 Selection of basic data.......................................................................................................................................5

Selection of type of heat exchanger......................................................................................................6 Tube dimensions...................................................................................................................................6 Coil pitch, distance of windings and coil length ....................................................................................7 Tube material ........................................................................................................................................7 Shell dimensions...................................................................................................................................7 Coil type ................................................................................................................................................7 Selection of media ................................................................................................................................8 Data Base .............................................................................................................................................8 Visual COIL...........................................................................................................................................9

COIL input mask and basic input menu...........................................................................................................10 Basic data selection ............................................................................................................................10 Specification sheet..............................................................................................................................10 Default values .....................................................................................................................................11 Set alpha tube-side .............................................................................................................................11 Set alpha shell-side.............................................................................................................................11 Data base............................................................................................................................................11 Geometrical data lock/edit ..................................................................................................................11

Properties and heat balance............................................................................................................................12 Manual input of properties "Free input"...............................................................................................12 Input mask and general heat balance.................................................................................................13

Geometrical data .............................................................................................................................................14 Coil pitch, distance of windings and coil length ..................................................................................14

Results and evaluation ....................................................................................................................................15 Condensation of any pure substances ............................................................................................................16

Data base 17 Using the data base.........................................................................................................................................17

Save Tubesheet..................................................................................................................................17 Load Tubesheet ..................................................................................................................................17 Data base / ->Standard.......................................................................................................................17 Data base / Select...............................................................................................................................17

Coaxial Tube Heat Exchanger (coiled double-pipe) in COIL 18 Calculation example of a coaxial tube heat exchanger with the COIL program..............................................18

Index 21

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Program description

Program features

Design of Tube Coil Heat Exchangers With the COIL program you can design, optimise and simulate tube coil heat exchangers. The exchangers may have a displacement cylinder to guide the flow around the coil or they may not have any internals. The coil pitch, the shell diameter and tube diameter are freely selectable. The coil may consist of a maximum of 5 parallel flown-through tubes. Shell-side flow is always forced flow. Flow direction might be cocurrent or countercurrent. You can also set the program parameters so that the program will only calculate with standard tube and shell dimensions (default values). This enables the constructor to optimise times of delivery or to reduce costs for storage by limiting the assortment of goods. Media must be single phase (liquid or gaseous) or condensing pure substances (pure substance condensation, isothermal condensation). The properties of the used media are provided by LV property modules and are determined for mean temperatures and pressures.

Condensation of multi-component mixtures is not possible with COIL.

Design of Coaxial Tube Heat Exchangers (coiled double-pipe) This option allows the complete thermal and hydraulic design of a coiled double-pipe heat exchanger according to VDI Heat ATLAS. Media are single-phase (liquid or gaseous) or condensing pure substances. The physical properties of the used media are provided by LV property modules and calculated for mean temperatures and pressures. Flow direction might be cocurrent or countercurrent.

Fundamentals

The calculations are based on the regulations of the VDI Heat Atlas

Chapter Gc: Heat transfer in flow through coils.

Chapter Lab: Pressure drop in flow through coils.

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Program structure

Structure of the program The program consists of units (modules) of our program system ATLAS, which are linked with each other by input and output variables. Each module represents an independent program provided with an input/output surface. There is no differentiation between a separate data input process and the calculation process. The program system ATLAS is a simultaneous dialogue/calculation system. Each entered value leads automatically to a processing step as long as the system is determined and the solution is found. The user himself/herself can decide which values are given and which values are calculated. The basic functions of this module and the editing rules are described in the manual of the ATLAS program system.

The modules of COIL

VDI Heat Atlas and properties modules: EGAS Properties of natural gas type H and L and of any composition

FRIG Properties of refrigerants

GLYC Properties of glycols (Antifrogene L, N, KF and SOL)

H2O Properties of water and steam

H2O Condensation of saturated steam

LUFT Properties of air

NH3 Properties of ammonia

OEL Properties of 12 machine oils

RGAS Properties of flue gas

SAWA Properties of sea water

TOIL Properties of thermal oils

SDAT Manual input of properties

BIER Properties of beer and wort *

CO2 Properties of carbon dioxide *

H2SO4 Properties and phase equilibrium of sulphuric acid *

HCl Properties of hydrochloric acid *

HFO Properties of heavy fuel oils *

HNO3 Properties and phase equilibrium of nitric acid *

HE Properties of helium *

N2 Properties of nitrogen *

N2H2 Properties of N2H2-Co mixtures *

NaOH Properties of sodium hydroxide *

PROP Thermodynamic calculation of properties of pure components and mixtures of up to 15 components according LV PROPER

*

SAC Properties of saccharose-water-solutions *

STAB General properties module for the definition of properties tables * * additional modules at extra charge.

Heat exchanger modules: ACOI Heat transfer around coils

COIL Design of coil heat exchangers

FN Correction factor for logarithmic temperature difference

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Operation

Starting COIL

Start Coil by ‘Programs’ / ‘COIL’ / ‘Coil type heat exchanger’

Menu ’Path’ In this menu you can determine the network paths for a network installation of COIL. COIL basic data (tubes, pitches, and shells), the tube sheet library and the properties module ‘STAB’.

Selection of basic data After starting the program the "Basic data selection" dialog box appears.

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In this dialog box you can specify the type of heat exchanger, the geometrical data and media and select company standards. The conception of the COIL program is that only few mouse clicks are needed to select type and basic design of the heat exchanger as well as tube-side and shell-side medium. The following basic data can be selected:

Description Contents Entry (example) Meaning Tube dimensions List of tubes used by the

manufacturer 25 x 2 coil-shell 12 coil diameter 250

Outside diameter of tube Wall thickness Distance Coil-Shell Coil Diameter

25 mm2 mm

12 mm250 mm

Coil pitch DH Coil pitch Distance of windings W Number of tubes

32 32 1

Coil pitch Distance of windings Number of tubes in the coil

32 mm32 mm

1Shell dimensions List of shells used by the

manufacturer 114.3 X 3.6 Outside diameter of shell

Wall thickness 114.3 mm

3.6 mm

Type of coil Type of displacement body

Coil with cylinder Coil without cylinder

Tube side medium property modules water Shell side medium property modules water

Selection of type of heat exchanger Select the type of heat exchanger you want to design

Coil Heat Exchanger Coaxial Heat Exchanger

Tube dimensions

Coils Several standard tubes according to DIN standards are given. The phrase 25 x 2 coil-shell 12 coil diameter 250 means:

Outside diameter of tube 25 mm Wall thickness 2 mm Minimum distance coil-shell and coil-cylinder 12 mm (This distance is not underrun while the

calculation is running. This value can be modified in the input mask afterwards.) Coil diameter 250 mm (This value is required to determine the standard shell, which is saved in the

program. The coil diameter is recalculated

Coiled double pipes Several standard tubes according to DIN standards are given. The phrase 20 X .75 / 12 X 1 / DW 220 means: External tube:

Outside diameter 20 mm Wall thickness 0,75 mm

Internal tube: Outside diameter 12 mm Wall thickness 1 mm

Coil diameter DW 220 mm The coil pitch DH may be entered freely. It must not underrun the value of the outside diameter of the external tube.

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Coil pitch, distance of windings and coil length COIL can calculate coil type heat exchangers consisting of a maximum of 5 parallel flown through tubes.

Coil pitch is always related to one tube. The distance of windings is the distance of the center of two adjacent windings of the coil. If the coil consists of only one tube, the distance is equal to the coil pitch. If the coil consists of n tubes (nR 5), the following relation of coil pitch DH and distance of windings is valid:

DH = nR · W

The coil length ls is calculated from the number of windings, N, number of tubes nR , coil pitch DH and the distance of windings W:

ls = N · DH + (nR-1) · W

Tube material Here you may select the tube material and the according thermal conductivity. The unit of the thermal conductivity is [W/(m·K)]. To save a new material and its thermal conductivity, simply enter the data in the fields 'Tube material' and 'Thermal conductivity' and then press the 'Save' button.

Shell dimensions Under shell diameter a lot of shells are predefined in accordance to DIN standards 2448 and 2458 for seamless and welded tubes.

The phrase 114.3 x 3.6 means

Outside diameter of shell: 114.3 mm

Wall thickness: 3.6 mm

If you have chosen "Free input / Design" for the shell the program automatically selects a shell from the list of shells during calculation of the heat exchanger.

Coil type By selecting the coil type, you select the design type of your coil heat exchanger, i.e. how the flow is guided around the coil. The following types can be designed:

Coil with displacement cylinder

Coil without displacement cylinder

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Selection of media Select the tube side and shell side media from the pull-down menu. The state of the media (liquid or gas), relevant for the calculation of the heat transfer, is set automatically. If you select 'Free input", "PROPER " or "STAB" (user-defined properties), you have to enter the state manually. If "Free input“ has been selected for one of the media in the “Basic data selection “ mask, the properties of this medium have to be entered manually (see Manual input of properties "Free input"). The COIL standard package comprises several properties modules. See: The modules of COIL You can enhance this list by adding further properties modules, which are not included in the standard package. The properties determination program PROPER (not included in the standard package) allows you to specify any mixtures of the data base and their components. Furthermore you can also enter properties manually by using the SDAT module (see Manual input of properties "Free input").

Data Base The "Data base" button allows you to transfer the geometrical data of an exchanger you have already designed from the data base to the program. A table is shown, where you can select the desired exchanger by clicking it. By clicking the "Load Tubesheet " button, the geometrical data are transferred to the COIL program. The "Finish editing" button closes the table and you switch back to the "selection of basic data ". Geometrical data you have already entered in this mask are overwritten and the geometrical data can not be changed manually. Please note that creating, editing and saving of a record is only possible in the COIL module (see Using the data base). After having finished the basic data selection, please confirm with OK.

Another selection mask is displayed

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Visual COIL

You can enter your system data (temperatures, pressures, mass flow or performance). These values can also be entered in the COIL input mask. Confirm your selection with OK and the COIL input mask is displayed.

TIP: Conversion of units A click on the unit or a double click on the input field the conversion of units is activated. Enter the values in the unit you have at hand; e.g., mass flow in kg/h. The value is immediately converted in all other displayed units. The unit with the activated checkbox is displayed on the mask and will be used for the documentation. Please confirm your input with 'ENTER'.

Flow direction Countercurrent / Cocurrent

Countercurrent flow

Heat exchangers with counter current flow have a higher thermal efficiency than cocurrent flow heat exchangers.

In countercurrent flow heat exchangers it is possible, that the outlet temperature of the cold medium exceeds the outlet temperature of the hot medium.

This is called 'Temperature Cross Over'

Idealized temperature profile in a countercurrent flow heat exchanger with temperature cross-over..

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Cocurrent flow

In cocurrent flow heat exchangers the outlet temperatures of the cold and the hot medium approach asymptotically.

Idealized temperature profile in a pure cocurrent flow heat exchanger (e.g. double pipe)

The cocurrent flow does not allow a switching of temperatures and the thermal efficiency is lower than in countercurrent flow. However there are some characteristics of cocurrent flow heat exchangers that are significant:

1. Cocurrent flow creates a more constant wall temperature than the countercurrent flow. 2. The maximum wall temperature is lower than in countercurrent flow. 3. This avoids unintended over or under temperatures. This is most important for food processing where

the temperature of the medium has to stay within a certain range to avoid protein coagulation.

COIL input mask and basic input menu With the COIL input mask, you control the calculation run. From this mask you can switch to all other modules of the software package. The mask comprises all required input possibilities for the calculation of a heat exchanger. The input values are also displayed on the masks of the according calculation module. They might be changed or entered in the modules as well. Switch to the module as described in the "ATLAS" manual ("ATLAS" menu - "chapter" or simply click the tab). The COIL module has a special menu called "Basic input".

Basic data selection This menu item brings you back to the "Selection of basic data".

Specification sheet With this menu item all data are transferred to MS EXCEL and displayed as specification sheet. You can rename all cells as you desire and save the sheet as template. Do not change the order of the cells, as the program otherwise does not write the data to the correct cell.

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Default values If the option is activated COIL uses preselected dimensions (e.g. the shell dimension of COIL12.TAB) and default values of COIL16.TAB for the design of heat exchanger. For example, if the user enters a new coil diameter during the optimization, COIL selects the shell, which just has enough space for this coil from COIL12.TAB. If the option is deactivated and a new coil diameter entered, you have to enter the shell dimensions manually. If the option is activated again, the heat exchanger is automatically recalculated. COIL uses again preselected dimensions from the COIL12.TAB.

Set alpha tube-side If the heat transfer coefficient in the tubes (alpha i) is known from other sources (such as measurements) and therefore doesn't need to be calculated by COIL, this value can be entered into the field "Heat transfer coefficient (inside)“ in the COIL input mask after clicking the option "Set alpha tube-side“. In this case the user interface "Clear value of variable" is not displayed, i.e. no recalculation to a dependent variable like e.g. the tube diameter is done. If you click again the option "Set alpha tube-side" the heat transfer coefficient in the tubes is calculated by COIL.

Set alpha shell-side If the heat transfer coefficient around the tubes (alpha a) is known from other sources (such as measurements) and therefore doesn't need to be calculated by COIL, this value can be entered into the field "Heat transfer coefficient (outside)" in the COIL input mask after clicking the option "Set alpha shell-side". In this case the user interface "Clear value of variable" is not displayed, i.e. no recalculation to a dependent variable like e.g. the tube outside diameter, coil diameter, coil pitch, etc. is done. If you click again the option “Set alpha shell-side“ the heat transfer coefficient around the tubes is calculated by COIL.

Data base You can save the geometrical data entered in the COIL input mask in a data base and load it for another calculation.

By clicking the button 'Save Tubesheet' the geometrical data (outside diameter of shell, wall thickness of shell, outside and inside diameter of tube, coil diameter, coil pitch, number of turns etc.) entered in COIL are saved to the data base. By clicking the button 'Load Tubesheet' the geometrical data highlighted in the table are transferred to the COIL input mask. With the button 'Finish editing' or by pressing the ESC key you switch back to COIL.

Geometrical data lock/edit If a tubesheet is loaded from the data base, it is always locked. This means the geometrical variables of the heat exchanger are fixed and can neither be overwritten in the input mask nor recalculated by the program. The fields concerned are highlighted in grey on the input mask. If modification of such variables is desired click the menu item ‘Geometrical data lock/edit’ to unlock the tubesheet for editing.

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Properties and heat balance

Manual input of properties "Free input" If "Free input“ has been selected for one of the media in the “Selection of basic data“ mask, the properties of this medium have to be defined. After entering the inlet and outlet temperature and the pressure on the COIL mask the SDAT module is activated automatically. Pressure and mean temperature are transferred already. Required data:

Liquids and gases (single phase media): For calculating the heat transfer and the pressure drop, properties at mean temperature and at wall temperature are required. At first start of SDAT the wall temperature is unknown. Please enter only the properties at mean temperature at first. As soon as the data input is complete, the program switches automatically back to the COIL mask. After the wall temperature has been calculated please switch to the SDAT module by clicking on the according tab strip and complete the properties at wall temperature. If you do not enter the properties at wall temperature, the values are replaced by the values at mean temperature for calculating the pressure drop and the heat transfer. In this case the accuracy of the calculation decreases. Especially with viscous media like oils greater errors might occur.

Condensation of pure substances When condensing pure substances, the properties of the vapour and the properties of the condensate at condensation temperature are required.

As soon as the data input is complete, the program switches automatically back to the COIL mask. If you have selected “Free input“ for both exchanger sides two SDAT modules are created.

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Input mask and general heat balance The first value block contains the information about the quantities, pressures and temperatures of both media. The values can be entered in any order. In most cases the mass flows and temperatures are already known, which means that the heat balance is fixed. However, the exact temperatures or quantities are specified only by the properties used in the program, i. e. the last temperature or quantity which remains to be entered is calculated by the program to complete the heat balance.

COIL input mask (heat balance)

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Geometrical data The second value block contains the geometrical data of the coil type heat exchanger. If you have already selected the tube and shell dimensions in the 'Selection of basic data' mask or if you have selected an exchanger from the data base, the geometrical data are already entered. If not, you have to enter the data manually.

COIL input mask (geometrical data)

Coil pitch, distance of windings and coil length COIL can calculate coil type heat exchangers consisting of 5 parallel flown through tubes. Coil pitch is always related to one tube. The distance of windings is the distance of the center of two adjacent windings of the coil. If the coil consists of only one tube, the distance is equal to the coil pitch. If the coil consists of n tubes (nR 5), the following relation of coil pitch DH and distance of windings is valid:

DH = nR · W

The coil length ls is calculated from the number of windings, N, number of tubes nR , coil pitch DH and the distance of windings W:

ls = N · DH + (nR-1) · W

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Results and evaluation The calculation ends as soon as the length of the exchanger is determined. This is the required length. The required length is the theoretical length, which is necessary to transfer the required performance. Now you have to enter the standard length (final length). With this length the exchanger is calculated again and a new required length is determined. The difference between the two lengths shows the ‘reserve’ of the design. Usually, the difference between final size and required size is expressed by a "substitute fouling rate". But this is not very specific. The "length reserve" is directly proportional to the area and represents a tangible measure of the reserve. After you have entered the diameter of the inlet and the outlet nozzle, the tube-side and shell-side pressure drop is being calculated.

COIL mask (results) The calculation can be directed by modification of the corresponding variables. The quality of the calculation can be enhanced e.g. by a "parameter study" informing how the exchanger responds when the process parameters are modified.

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Condensation of any pure substances The COIL program can calculate a condenser with condensation of any pure substance. For the calculation of the condensation process it is important that the vapour enters the condenser with saturated steam temperature, which means not superheated, and that the condensate leaves the condenser with the same temperature, which means not subcooled. If the vapour enters the condenser superheated and the condensate leaves the condenser subcooled, the condenser has to be divided into three zones. The desuperheating zone, the condensing zone and the subcooling zone. These zones have to be calculated separately with the COIL program. The complete transfer area is the result of the areas of the single zones. If ‘Saturated steam’ or ‘NH3 condensation’ or ‘CO2 condensation’ have been selected in the ‘Basic data selection’ dialog box as condensing medium, a condensation of saturated steam (water steam) resp. ammonia or Co2 is presumed and COIL selects the condensation set-up to calculate the heat transfer. The condesation pressure Psat or the condensation temperature is required as input value. The properties of the steam and the condensate are calculated automatically. For any pure substance to be condensed, "Free input" has to be selected for the condensing medium and ‘Condensation’ for the for the physical state in the "Basic data selection". I In the COIL input mask or in the ‘Visual COIL’ form, the condensation pressure as well as the condensation temperature have to be entered. Then the program switches to the SDAT module automatically. Enter the properties of the condensate (boiling liquid) into the upper part and the properties of the vapor and the enthalpy of evaporation at the lower part. As soon as you have entered all required data, the program switches back to the COIL mask. The pressure drop on the condensing side is not calculated.

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Data base

Using the data base

Save Tubesheet This button is only visible if the data base has been called up by the COIL program. All geometrical data of the exchanger entered in the input mask of coil are transferred to the data base.

Load Tubesheet The highlighted record is used in the current calculation of COIL. The data are transferred to the COIL program and all data in the input mask are overwritten.

Data base / ->Standard The tube sheet data can be distributed over different data bases. All operations refer to the currently active data base, the name of which is entered in the field below "Data base". The standard data base is the one used when activating the form. This data base is indicated by the yellow background colour in the data base field. This setting can be changed by pressing the button ‘->Standard’. If the standard data base does not exist during the calling up or if no one has been selected yet (in this case coil.mdb is used), automatically a new one with the corresponding name will be created.

Data base / Select With the help of this function another data base can be loaded. If no file extension has been given, ".MDB" is automatically added. If a data base that has been entered does not exist, automatically a new one is created by copying the copy pattern file "COIL_LEER.MDB".

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Coaxial Tube Heat Exchanger (coiled double-pipe) in COIL

Calculation example of a coaxial tube heat exchanger with the COIL program

The entries for the calculation of a coaxial tube heat exchanger are done in the mask 'Basic data selection'.

This mask is the first mask to appear after program start. By selecting the option Coaxial tube heat exchanger' in the ‘Heat exchanger type’ field, the calculation is initialized. There are several tubes and pipes in the database which can be selected in the selection boxes 'Internal tubes' and ‘External tubes’. The data of these tubes (outside diameter and wall thickness) can be saved. If you want to use tubes which are not listed in the selection box, you can overwrite the values for outside diameter and wall thickness directly in the fields. You can change the values at a later time in the COIL mask as well. Select the tube-side and shell-side media and confirm your selection by pressing 'OK'. The next mask 'Visual COIL' is displayed. In this mask you may enter your system data for the tube-side and shell-side media. Confirm your entries with 'OK'. The program switches to the COIL input mask.

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Here you may complete or correct your system data (pressure, temperature, mass flow).

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If your system data are complete, the calculation is started and the required tube length is calculated. >> Enter the final tube length which is the tube length of the manufactured heat exchanger. The exchanger is recalculated with this tube length. Please adjust the final bundle length to the required bundle length. The difference between required and final bundle length is the ‘Overdesign’. Alternatively you might enter the final heat exchanger area, the final number of windings or the final total coil length (height of the coil).

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COIL Manual Index 21

Index

B

basic data 6, 8, 10, 12, 14 Basic data 16

D

default 3, 11

F

Free input 16

G

geometrical data 6, 8, 11, 14, 17 Geometrical data 14 Geometry 14

H

heat balance 12, 13 heat transfer coefficient 11

L

LEER.MDB 17

M

mdb 17 media 8, 12 modules 3, 4, 6, 8, 10, 12

P

properties 3, 4, 8, 12, 13, 16

R

reserve 15 Results and evaluation 15

S

SDAT 12 shell dimension 3, 11, 14 standard 3, 6, 8, 15, 17

U

Use record 8, 11, 17