Wellford Seminar13

7/27/2019 Wellford Seminar13

1/17

E f f i c i e n t E n er g y R e c o v e r y S o l u t i o n s S i n c e 1 98 1

A S H R A E S e m i n a r 1 3

A R I E n e r g y R e c o v e r y V e n t i l a t i o n P r o g r a m

O v er v i e w : H o w t o u s e t h e r a t i n g s .

B e d e W . W el l f o r d , V .P . Ma r k e t i n g , A i r x c h a n g e , In c .

J a n u a r y 2 6, 2 00 3 C h i c a g o , I l l i n o i s


2/17

A RI Di r ec t o r y L i s t i n g


3/17

Iden t i f i ca t i on and

A d d i t i o n al In f o r m at i o n

Model designation.

Rated airflow.

Purge if used.

Tilt angle for heat pipes.


4/17

Cer t i f i ed and App l i ed Rat i ngs

Certified Ratings are at specific conditions as required byStandard 1060.

Certified Ratings can be useful for comparison, but their

greatest value is to support application ratings.

Application Ratings are for the range of operating conditions,

catalogued or otherwise. They must be consistent with the

Certified Ratings.

Application Ratings are used to evaluate performance in a

given design and/or climate.

Both catalog data and performance software should provideresults that are consistent. Confidence in the Application

Ratings comes from the Certified Ratings.


5/17

Therm al Per f o r manc e and

Pressure Loss

Sensible, Latent and Total Effectiveness at 100% and 75% of

rated flow.

Net Effectiveness ratings are corrected for leakage effects.

These ratings are repeated for both winter and summer

conditions.

Pressure Drop at 100% of rated flow.

And.


6/17

A i r f l o w an d L eak ag e

Two leakage characteristics at three different pressures

EATR is exhaust air transferred from return to supply.

OACF is the ratio of outdoor air to supply air.

The ratings at three different pressure conditions provide

confirmation of the shape of these leakage curves.


7/17

Ef fec t iveness Sensible effectiveness.

Latent effectiveness.

Total effectiveness.

Effectiveness ratings and tests are at balanced flow and 0

WC pressure differential between return and supply.

At 95/78 outdoor and 75/63 indoor summer conditions.

At 35/33 outdoor and 70/58 indoor winter conditions.

Determine which ratings are significant for your application.

Measured effectiveness determines the leaving air

conditions.


8/17

Net Ef fec t iveness Rat ings

Adjusted for the impacts of leakage as required.

Net effectiveness ratings provide information on the

actual energy recovered.

Small differences may not show up in the certifiedratings due to program tolerances.

Significant impacts do show up in the certified net

ratings.

Modeling and submittals should provide the net values

for the application. Net airflow too!


9/17

Ef fec t iveness

Definition of Effectiveness:

Effectiveness is not efficiency.

Effectiveness can be misleading:

Small differences are not significant.

Watch out for unequal flows!


10/17

Ef fec t iveness

The impact of unequal flows on effectiveness:

The effectiveness is correct, but it must be applied to

the minimum flow to calculate energy impacts.


11/17

Pressure Loss

Delta P in inches of water column across the supply side

of the heat exchanger at 100% of rated flow.

Certified Ratings are at standard air conditions in SCFM.

Application ratings may be provided for a variety of

airflows in SCFM.

Applied performance should be calculated at applied

conditions in ACFM.


12/17

E A T R

EATR is the exhaust air transfer ratio (air from the return

that ends up in the supply, expressed as a percentage of

the supply air).


13/17

Us i n g E A T R

Use EATR to evaluate component selection, fan

arrangement and fan size to meet ventilation

requirements.

Adjust the supply airflow to account for any volume of

return air in the supply.

Example: if EATR is 5%, and outside air requirement is

2000 CFM:

Supply CFM=Required OA CFM (1+EATR)=

2000 (1+0.05)=2100 CFM

In this example 2000 CFM is outside air

and 100 CFM is recirculated return air.


14/17

O A C F

The ratio of outdoor air to supply air (expressed

as a ratio).


15/17

Us i ng O A C F

Use OACF to adjust the airflow at the hood (or the

supply fan in a push supply arrangement).

Air that leaves the supply airstream due to seal

leakage and purge volume is in addition to the

outside air in the supply airstream. Outside Air CFM=Supply Air CFM (OACF)

Example: Supply Air CFM is 2100 and OACF is 1.1:

OA CFM=2100 (1.1)=2310

2310 CFM must be brought in at the hood.


16/17

Benef i t s o f Us in g Cer t i f i ed Rat in gs

The component will perform as selected. Fans can be correctly sized to account for EATR and

OACF.

Design load reductions, and therefore system size, will

be accurate.

Operating energy savings can be accurately predicted.

Humidity performance of the component can be

characterized at conditions of interest. Other components

of the system can then be selected accordingly.

The system will perform as designed.


17/17

E f f i c i e n t E n e r g y R e c o v e r y S o l u t i o n s S i n c e 1 9 81

Thank you!

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Wellford Seminar13