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ekumaran_m
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Join Date: Dec 2009
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Thermal Management - Car Air Conditioner Design and Compressor Selection

12/22/2009 1:03 PM

how to calculate the heat generated by the person sitting in the car i.e air conditioned? Based on this how to select a HVAC compressor if the temp inside cabin is to be maintained at 25 deg C and there are 4 persons inside? the car size is 1.6m width , 3.5 m length and 1.5m height. This is related to Thermal management .

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Tornado
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#1

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/22/2009 5:01 PM

Humans generate about 750 Btu/h; more if active, probably a bit less under your conditions. THis will be a minority of your load, though; heat transmission through the envelope is (usually, anyway) quite a bit more.

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bioramani
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#2

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/23/2009 12:53 AM

A sitting adult may generate about 100 W. The external heat input will be much more than from 4 adults in side a car.

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ekumaran_m
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#5
In reply to #2

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/24/2009 10:52 AM

thanks a lot for ur reply , it ll be helpful . what are the other loads we can expect for the air conditioner. do u mean by radiation heat, or anything else . please let me know

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bioramani
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#6
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Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/24/2009 9:38 PM

The total surface area is about 15 sq.m. The worst case situation is with the car in full sun. A car AC is not designed for when it is parked (Solar input maximum). In South India solar insolation is about 800 W /Sq.m most of the year. Some assumptions have to be made. 1. Av. area exposed to sun=50% of 15 = 7.5 sq.m. 2. Av. solar input = 25 % of insolation for a moving car = 800x7.5x0.25 = 1500 W 3. Occupancy input = 400 W 4. Extra for input from engine side = 200 w (Guesstimate) Total 2100 W heat load. AC electrical load may be about a third of this as AC is a heat pump and only moves heat from hotter to colder and does not generate cold. This is an off the cuff estimate. Indicates likely order of magnitude. Detailed calculations will be needed for actual design of system.

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ekumaran_m
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#7
In reply to #6

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/24/2009 10:20 PM

thanks a lot sir..

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mrswamy
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#3

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/23/2009 1:43 AM

The occupants in a conditioned space give out heat at a metabolic rate that more or less depends on their rate of working. Total heat comprises of sensible and latent and depends upon ambient dry bulb temperature. Lower the DBT greater the sensible heat. Typical values are given in any HVAC hand book. To select a compressor you need to calculate the total heat load of the car as per the HVAC procedures. You have to refer ASHRAE heat load calculation procedure. Calculate the total cooling load and then select the system.
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ekumaran_m
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#4
In reply to #3

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

12/24/2009 10:48 AM

Thanks a lot sir cld u please suggest me websites where i can find the HVAC handbook or ASHRAE procedure online . i have got some idea which will help me in solving the problem. PLease help me Further...

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Anonymous Poster
#8

Re: Thermal Management - Car Air Conditioner Design and Compressor Selection

11/01/2010 12:16 PM

Dear sir, i am working in subros ltd. it is a auto air conditioning manufacturing company. pls send me the details of design of thermal management part of car air conditioner. thanks ajay email id- ajaychoudhary8@gmail.com
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Anonymous Poster (1); bioramani (2); ekumaran_m (3); mrswamy (1); Tornado (1)

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