calculating the capacity of an air conditoner

[PaulLag]

Hi there
Hope everybody is fine.
I am here contacting you in order to clarify a big doubt I have concerning a test to realize.

Following is the topic.
I’ll try the best to explain it, since it is not simple:

We have in a closed test room an air-air heat pump, that works with refrigerant R410A.
We’d like to test it with an air ambient of 19F, while the heat pump would have an evaporating temperature of 14F
High pressure side of the heat pump will be ducted in order to push hot air out of the room

Currently this is not possible, since into the room there is only an air conditioner with water capable of getting the environmental air up to 39F.

I have been suggested is to add an additional air conditioner in order to lower the temperature from 39F to 19F.
My question now is as follows:

how can I calculate the capacity this new air conditioner need to give in order to get the ammbient air temperature down to 19F ?
In other words, what do I need to consider in order to calculate the thermal load of the room

Point is: when air is lower than 39F, the current air conditioner is no more useful, since air is at a lower temperature than water (and therefore it is not useful).
On the other hand, the heat pump is working so that specifically the evaporator part will decrease the ambient temperature down to a certain temperature, let’s call it T_air_outlet_heat_pump

May I assume that the capacity needed to lower the temperature up to 19F is
Heat_pump_air_flow*cp*density*( T_air_outlet_heat_pump -19) + room dispersion+ electrical power of compressor ?

where
Heat_pump_air_flow is the air flow of the evaporator part of heat pump


Please, is there something I am missing ?
Can anybody give me an help concerning this topic ?

Thanks !!

 

[Compositepro]

Do your testing in a walk-in freezer, which is readily available. There are significant differences between air conditioners, refrigerators, and freezers. You don't want to spend your time learning the nuances of designing them when your goal is just to test something else. Anything operating below freezing for any significant time must be capable of defrosting the evaporator coil periodically.

The freezer needs at least twice the refrigeration capacity than the device you are testing.

 

[itsmoked]

Air conditioners do not cool air down to 19F. Nor do refrigerators. You need a freezer as comp suggests.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

There are testing companies that do this sort of thing for a living. Moreover, their equipment is calibrated, tested, and certified to meet their performance requirements.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[MintJulep]

Typically when testing evaporator capacity you add LOAD to the test chamber that contains the evaporator so that you can confirm that your equipment has the necessary capacity.

You would rely on the equipment under test for cooling the test chamber.

 

[dbill74]

Simply "adding" another air conditioner is not going to get the test chamber down to 19F. You need a unit specifically designed to reduce the air temp to 19F.

 

[IRstuff]

A typical A/C is designed to supply around 55F air at the evaporator, which is a LONG way from 19F

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm