How to determine the suitable air-conditioning system

[Terrywarner]

I always encounter such question for my design and have no idea which kind of air-conditioning system best suit to my design. I have been confused with air-conditioning system like Water cooled Chilled water system, Air-cooled split unit system, etc when I handled some of the project like Hospital, library, and shopping mall. I have consult a handful of engineers, but their answers seem clashing with each other.

My Questions are summarized as follow:

1. How to choose a suitable air-conditioning system based on the BTU?
2. Which should I depend most the BTU or the Tons of refrigerant?
3. What are the range of air-conditioning system available for all building design(ie chilled water system, aircooled or water-cooled)?
4. How big an air-conditioner or air handling unit do I need?

[johnnychin]

I think it should be based on the size of the project, whether the HVAC system are likely to be expanded in future or operation wise required maintenance on chilled water system.
Take a look on these information, I think you might get some idea out of them.
http://www.greenair.webege.com
http://www.hvacnews.com
and some related software
http://www.flycarpet.net/en/download.asp
http://www.freecalc.com/

[Brian_UK]

2. Which should I depend most the BTU or the Tons of refrigerant?

Use BTU or kW.

Ton of refrigeration American is about 10% less than Tonne (metric) of refrigeration,; so you need to ensure that you know which ton they are using.

[dan2010]

Use BTU or kW.

Ton of refrigeration American is about 10% less than Tonne (metric) of refrigeration,; so you need to ensure that you know which ton they are using.


But which ton of refrigeration we gonna choose if my product is carrier while I'm going to deal with a client from uK?

[pumperbee]

Use BTU or kW.

Ton of refrigeration American is about 10% less than Tonne (metric) of refrigeration,; so you need to ensure that you know which ton they are using.

What is the reason we have to use separate terms of tons of refrigeration? In which case this terms apply? I heard about the
Standard Ton of Refrigeration America? What is the difference?

[frozenbit]

What is the reason we have to use separate terms of tons of refrigeration? In which case this terms apply? I heard about the
Standard Ton of Refrigeration America? What is the difference?

For what reasons and the terms of refrigeration you gonna deal with are all depending on the requirement of the client and project manager.


I can only share a little thing about the terms ton of Refrigeration.

The U.S. commercial ton of refrigeration states that a rate of extraction of 200 Btu / Minute (3516.857 j/sec) or it can be the frozen rate of a ton of ice of specific latent heat 144 Btu per pound in 24 hours from water at the same temperature. Symbol CTR, or CTR(US).

The U.S. standard ton of refrigeration is specifically referred to as an amount of cooling not a rate. Removing 288,000 Btu commercial ton of refrigeration is approximately a standard ton refrigeraion for the cooling provided by melting 2009.1 pounds of ice. Rejecting heat at a commercial ton results in a standard ton removed in one day.

The British commercial ton of refrigeration looks alike the American, however, it use a bigger ton of ice (2240 pounds).

Simply,

A tonne of Refrigeration is about 13173Btu/H which is also equivalent to 13,898 kJ/H and 3.861 kW

Meanwhile, a ton of refrigeration is about 12000Btu/H and is also equivalent to 12,661 kJ/H and 3.517 kW

[Terrywarner]

I have flip through most of the catalogue provide by air conditioning manufacturer. But none of them have a definite answer for the internal static pressure of a AHU. All I know is around 1.5 inWC for AHU below 3,000CFM. But what about those above 10,000 CFM. Any idea to calculate static pressure internally?

[Brian_UK]

Static pressure requirement depends entirely on the ductwork attached to the fan.

Design your duct system, perform the calculations for system resistance and order your fan accordingly.

As far as which unit to use for the AC I would stick with kW, if whoever you order from does not understand kW or how to convert to their preferred units then I would select another supplier.

[hamadalx]

Every Discussion in this forum is( lesson)
Best regards

[ref717]

Static Pressure is a measure of the resistance to movement of forced air thru a system or installation, caused by ductworks, inlets, louvers, etc. In air movement systems, SP is usually measured in inches of water gage.

In selecting an AHU, know first your CFM requirement, then select your fan with the correct SP based on your system resistance calculations.

The performance of all fans and blowers is governed by certain rules of physics known as the Fan Affinity Laws. You can use this formula as guide only :

2
( CFMnew ) = SPnew
(CFMexisting) SPexisting

goodluck..