Walkl-in cooler/freezer. How to choose the equipment

[krgari]

Hi everybody! It`s a first time I`m posting here, but I saw a lot of intresning questions and answers.
So! My question is about sizing up equipment for walk-in cooler/freezer.
Let`s say I calculated all the loads we have in the room : walls transmission, air change, motors, people, product. Total say 250 000BTU/24Hr + 10% Safety Factor =275 000 BTU/24Hr.
Divided by No. of operating Hours 16 for cooler , (18 for freezer ), I`m getting 275 000 : 16 =17 187.5 BTU/Hr
Is that correct till now? If yes what is next.
What size will be my condensing unit, evaporator coil and TX valve.let`s say we are talking regular storage cooler 25 F evap. temperature.

[Josip]

Hi, Krgari

Welcome to RE.

Your numbers are correct, but the question is how you obtain your numbers

What size is your room, wall panels quality, type and quantity of goods to cool....

If you can tell us little more maybe we can help a little more

Evaporator(s) are the same or bigger size as your load 17200 BTU/h (5kW), and.....

Best regards, Josip

[munesh]

Any Idea about the piezoelectric cooling. Need some information on the same.

[Samarjit Sen]

Dear krgari,

You have left out the most important thing and that is what is the temperature of the room you propose to maintain. Next is what is the product and what is the temperature at which it is coming in and what is the required pull down time.

Based on this and the information that Josip has asked, can a selection of the equipments be made.

[Peter_1]

Any Idea about the piezoelectric cooling. Need some information on the same.

Better post this in another section.

[Brian_UK]

Any Idea about the piezoelectric cooling. Need some information on the same.

Try the universal brain and click on Google, we had too so you can try as well.

Checking through your posts here it seems that you are trying to bypass the normal marketing research methods. You must not expect everyone else to resolve your marketing needs, go out and find the information yourself then when you have a less demanding question you may get a better response from the forum.

[krgari]

Dear krgari,

You have left out the most important thing and that is what is the temperature of the room you propose to maintain. Next is what is the product and what is the temperature at which it is coming in and what is the required pull down time.

Based on this and the information that Josip has asked, can a selection of the equipments be made.

I understand all that. But I wasn`t talking about some specific room. Just want to have an idea how it`s beeing calculated. Let`s say you choose the evaporator based on total load of product, room, ......etc.
You choose TX valve size based on A, B, C, numbers. ETC.
I can`t find any books explaining this in details.
I know there are programs that can be used for caculation, but I want to know how to do it on piece of paper.

[The MG Pony]

Cool pack is handy

[Peter_1]

Choose a storage temperature
Determine load of the room itself.
Determine load of the product entering the room.
Determine latent heat - if any - of the stored load.
Calculate the average hourly load. (16 hours running time is common used)
Select the best gass for your application.
Select an evaporator which can handle this average load working at the correct DT. (between 5 and 10 K)
Select the proper TEV for this load.
Seelct a compressor for the chosen gass, giving the right capacity at the calculated evaporating capacity (right DT) for the expected outside conditions.

That's it.

[US Iceman]

...but I want to know how to do it on piece of paper.

Bravo. Finally someone wants to learn it, instead of using a PC program. My hats off to you.

Here is a link to some downloads you might want to review for related material. The engineering manual has a procedure listed in it you can follow.

http://www.heatcraftrpd.com/service/handbooks.asp

[US Iceman]

My previous post was for the load calculations. The following is from a recent reply to another question from a different RE member.

When you select the compressor, you have to be careful. The suction and discharge lines will have pressure loss due to the refrigerant flowing through them. When selecting the compressor you have to allow for this.

If the evaporating temperature is 30F, you need to calculate the pressure loss of the suction line to achieve accurate compressor selections.

A quick example: if the evaporating temperature is 30F (for a room temperature of 40F), you will need something like a 2 degree DT penalty to allow for the suction line loss. This means if your evaporting temperature is 30F, the actual temperature you use for the compressor selection is 30F - 2 =28F, so you select the compressor at 28F temperature for 12,000 Btu/hour.

You have the same thing on the discharge side of the compressor. If the discharge line is allowed a 2 degree DT penalty then your actual condensing temperature becomes: 86F air entering + 2 degree DT penalty + 20 Degree DT for the condenser = 108F condensing temperature.

Now you can select the compressor for 28F evaporating temperature and 108F condnsing temperature.

I'll have to come back and do the unit conversions.

[krgari]

[QUOTE=US Iceman;59338]Bravo. Finally someone wants to learn it, instead of using a PC program. My hats off to you.

Here is a link to some downloads you might want to review for related material. The engineering manual has a procedure listed in it you can follow.


Thanks Iceman! I`t`s very helpfull site, and a lots of information. I hope many of this site visitors will need this info.
I`m in this field for last 6 years, and only in service.
Now I`m planning to go on my own, so have to learn more.
Thanks again!

[Samarjit Sen]

Dear Krgari,

If you are keen to learn more about the Cold Room heat load, I would suggest you refer to Ashrae Handbook on Refrigeration. This is a very good source of detail information.

With best wishes,