View Full Version : Refrigeration help

25-03-2017, 12:41 PM
Hey, I am new here.

I am looking for help and hints on how to solve my refrigeration assignment.

Probably it isn't complicated for you, but my course is more building services orientated and that is the first that I came up with sizing of evaporators for coolers. Any help much appreciated.

Size the evaporator for a drink cooler designed to hold 144 cans of a drink which has a specific heat capacity of 3.2 kJ/kgK. The density of this drink is 1kg/litre. The unit is to be constructed using glass fibre insulation (k = 0.036W/mK) with x= 25mm. This task must take freshly delivered product at 32.2C to the temperature of 3.3C .

Many Thanks ,

26-03-2017, 12:09 AM
Hello and welcome to the Forum.

It wouldn't be right for us to give you the answers to you college work assignments but if you want to post your working out...or thoughts on the questions..,we could point you in the right direction.
The only way to learn is to try...not just copy answers

26-03-2017, 04:02 PM
Hey :)

So I got to the point, where I sized the actual size and volume of the unit (0.072m3). I also calculated resistance to heat flow through a given thickness of material which is 0.694 m2K/W. Using this value I estimated heat loss and cooling load which is 2.8 kW. I am assuming that if everything is calculated right, I would have to select the refrigerant. (I need to pick one of the three following refrigerants : HR600a, HFC-134a, Suva 407C). and I that is the point where I am not too sure what to do next..I am not asking for the answer of the coursework. I am asking for hints or simple steps that need to be followed to work this out. :)

Rob White
26-03-2017, 07:27 PM

Consider the evaporating temperature related to the product temp, with air
10degs difference is reasonable. With the evaporating temp of -6 / -7 you need
to work out which refrigerant will give you the best performance.

You do not mention ambient temperatures but your product arrives at 32degs?
Is that the ambient?

Are you allowed to use pH charts because if you plot your numbers on a pH chart,
one for each refrigerant you will be able to plot efficiencies of each refrigerant.