HVAC

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Monday, March 3, 2008

About Us
www.hvacindia.org.in is a portal launched by ISHRAE (Indian Society of Heating, Refrigerating and Air Conditioning Engineers), to promote Heating, Ventilation, Air-Conditioning and Refrigeration (HVAC and R) industry in India. ISHRAE is an associate of ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers). The portal is sponsored by leading companies.

The portal is co-ordinated by Rajeev Kakkar

Cooling load calculation

Space Heat Gain and Space Cooling Load
Space heat gain is the rate at which heat enters a space, or heat generated within a space during a time interval.
Space cooling load is the rate at which heat is removed from the conditioned space to maintain a constant space air temperature.
Figure 3 shows the difference between the space heat gain and the space cooling load. The difference between the space heat gain and the space cooling load is due to the storage of a portion of radiant heat in the structure. The convective component is converted to space cooling load instantaneously.

How to calculate cooling/ heating load

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Thursday, December 6, 2007

Hourly Load Calculation Program

"Indian Interface to EnergyPlus:
HLCP Hourly Load Calculation Program HLCP (Hourly Load Calculation Programme) is a graphical user interface for design-day and hourly load calculations for Indian cities, meant to be used with the Energy Plus simulation engine. HLCP is a for-purchase program.

For details, please go to http://www.hvacindia.com/hlcp/ "http://gundog.lbl.gov/dirun/28nov.pdf

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Saturday, December 1, 2007

Calculating The Size of a Server Room Air Conditioner

This article is a quick guide to how to work out your requirements for an air conditioning unit for your Server Room or Data Center*.
In principle it’s easy to calculate the size of air conditioning unit you need for your Server Room, just add together all the sources of heat and install an air conditioning unit that can remove that much. In practice it’s rather more complicated.

Fire regulations often require that Server Rooms have levels of insulation far above that of a normal office. Providing sufficient cooling is essential to ensure reliable running of servers, routers, switches and other key equipment. Failure of the air conditioning can have serious consequences for the equipment itself and for your company. Early warning of problems and spare capacity in the cooling system are both highly desirable.

Calculating Heat Load
The amount of heat generated is known as the heat gain or heat load. Heat is measured in either British Thermal Units (BTU) or Kilowatts (KW). 1KW is equivalent to 3412BTUs.
The heat load depends on a number of factors, by taking into account those that apply in your circumstances and adding them together a reasonably accurate measure of the total heat can be calculated*.

Factors include:
The floor area of the room
The size and position of windows, and whether they have blinds or shades
The number of room occupants (if any)
The heat generated by equipment
The heat generated by lighting

Floor Area of Room
The amount of cooling required depends on the area of the room. To calculate the area in square metres:

Room Area BTU = Length (m) x Width (m) x 337

Window Size and Position
If, as is quite common, your Server Room has no windows, you can ignore this part of the calculation. If, however there are windows you need to take the size and orientation into account.
South Window BTU = South Facing window Length (m) x Width (m) x 870
North Window BTU = North Facing windows Length (m) x Width (m) x 165

If there are no blinds on the windows multiply the result(s) by 1.5.

Obviously if you are in the Southern Hemisphere you would swap the conversion factors as the heat on North facing windows is then greatest.
Add together all the BTUs for the windows.
Windows BTU = South Window(s) BTU + North Window(s) BTU

Occupants
Purpose built Server Rooms don’t normally have people working in them, but if people do regularly work in your Server Room you will have to take that into account. The heat output is around 400 BTU per person.

Total Occupant BTU = Number of occupants x 400

Equipment
Clearly most heat in a Server Room is generated by the equipment. This is trickier to calculate that you might think. The wattage on equipment is the maximum power consumption rating, the actual power consumed may be less. However it is probably safer to overestimate the wattage than underestimate it.

Add together all the wattages for Servers, Switches, Routers and multiply by 3.5.
Equipment BTU = Total wattage for all equipment x 3.5

Lighting
Take the total wattage of the lighting and multiply by 4.25.
Lighting BTU = Total wattage for all lighting x 4.25
Total Cooling Required
Add all the BTUs together.

Total Heat Load = Room Area BTU + Windows BTU + Total Occupant BTU + Equipment BTU + Lighting BTU

Total Heat Load x 2 (Factor of Safety) is the Cooling Load

This is the amount of cooling required so you need one or more air conditioning units to handle that amount of heat.
So what size of unit do I need?
Small air conditioning units have a cooling capacity of between 5000 and 10000 BTUs. Small units may fit in windows, venting to the outside world.
Larger units may be rated in tons of cooling. 1 ton of cooling is equivalent to 12 thousand BTUs.

* Disclaimer: This calculation is intended as a rough guide only. Complete accuracy cannot be guaranteed. Before you decide on an air conditioning unit you should commission an audit from a suitably qualified air conditioning equipment specialist or installer.

About the Author
Denis Laverty possesses more than 17 years experience in network management and communications, Denis has been involved with network management applications from the early DOS days; as product trainer, technical author and QA Director. In 2003 he co-founded OPENXTRA together with Jack Hughes and serves as its Managing Director.
About OPENXTRAOPENXTRA Limited is a privately held network management VAR based in the UK. This blog is here to help you get the most out of our products and network management in general. Read more about OPENXTRA and this blog.
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Saturday, September 15, 2007

Heat Load calculations

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How Air conditioning works

by Marshall Brain
Inside This Article
1.
Introduction to How Air Conditioners Work
2.
Air-conditioning Basics
3.
Window AC Units
4.
Split-system AC Units
5.
Chilled-water and Cooling-tower AC Units
6.
Lots More Information
7.
See all Household Appliances articles
Air-conditioning BasicsAn air conditioner is basically a refrigerator without the insulated box. It uses the evaporation of a refrigerant, like Freon, to provide cooling. The mechanics of the Freon evaporation cycle are the same in a refrigerator as in an air conditioner. According to the Merriam-Webster Dictionary Online, the term Freon is generically "used for any of various nonflammable fluorocarbons used as refrigerants and as propellants for aerosols."
Diagram of a typical air conditioner
This is how the evaporation cycle in an air conditioner works (See How Refrigerators Work for complete details on this cycle):

The compressor compresses cool Freon gas, causing it to become hot, high-pressure Freon gas (red in the diagram above).
This hot gas runs through a set of coils so it can dissipate its heat, and it condenses into a liquid.
The Freon liquid runs through an expansion valve, and in the process it evaporates to become cold, low-pressure Freon gas (light blue in the diagram above).

This cold gas runs through a set of coils that allow the gas to absorb heat and cool down the air inside the building.
Mixed in with the Freon is a small amount of a lightweight oil. This oil lubricates the compressor.
So this is the general concept involved in air conditioning. In the next section, we'll take a look inside a window unit.
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FAQ's

HVAC (pronounced either "H-V-A-C" or, occasionally, "H-VAK") is an initialism/acronym that stands for "heating, ventilation, and air conditioning".

HVAC is sometimes referred to as "climate control" and is particularly important in the design of medium to large industrial and office buildings such as sky scrapers and in marine environments such as aquariums, where humidity and temperature must all be closely regulated whilst maintaining safe and healthy conditions within. In certain regions (e.g., UK) the term "Building Services" is also used, but may also include plumbing and electrical systems. Refrigeration is sometimes added to the field's abbreviation as HVAC&R or HVACR, or ventilation is dropped as HACR (such as the designation of HACR-rated circuit breakers).

Heating, ventilation, and air conditioning is based on the basic principles of thermodynamics, fluid mechanics, and heat transfer, and to inventions and discoveries made by Michael Faraday, Willis Carrier, Reuben Trane, James Joule, William Rankine, Sadi Carnot, and many others.

The invention of the components of HVAC systems goes hand-in-hand with the industrial revolution, and new methods of modernization, higher efficiency, and system control are constantly introduced by companies and inventors all over the world.

The three functions of heating, ventilation, and air-conditioning are closely interrelated. All seek to provide thermal comfort, acceptable indoor air quality, and reasonable installation, operation, and maintenance costs. HVAC systems can provide ventilation, reduce air infiltration, and maintain pressure relationships between spaces. How air is delivered to, and removed from spaces is known as room air distribution.[1]

In modern buildings the design, installation, and control systems of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally "size" and select HVAC systems and equipment. For larger buildings where required by law, "building services" designers and engineers, such as mechanical, architectural, or building services engineers analyze, design, and specify the HVAC systems, and specialty mechanical contractors build and commission them. In all buildings, building permits for, and code-compliance inspections of the installations are the norm.
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HLCP FAQ's

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