Heat transfer coefficient
We had to deal with the amount of heat contained something and the amount of heat transferred from one object to another. As can be measured in BTU. In BTU deals with the"how much" the idea of the heat. It is dedicated to the heat content and the change in enthalpy.
Temperature-enthalpy diagram show the heat capacity of liquid at different conditions. They also use BTU measure the change in enthalpy between the two conditions. Later we will see how BTU also used in a similar way, the pressure-enthalpy diagram for refrigerants.
We have not dealt with how fast the transfer of heat between two objects. In mechanical refrigeration work, the question "how fast is very important. We use Btuh measure the rate of heat transfer. Btuh is a short way of saying BTU / hour. The most important issue in dealing with heat gain in the building (its cooling load) not how much heat entering it, but how much heat, typing it each hour (Btuh).
In other words, "How fast heat supplied to the building?"
The system, which removes heat more slowly, than will allow the accumulation of heat into space. The temperature will rise and comfort will be lost.
In Btuh is the basic unit of expression heat transfer coefficient for both loads of space and equipment capacity. It is not only the device, however. Sound is much more the unit of measure used to Express the approximate load space, the ability of a system, and power piece of refrigeration equipment.
The term "Tons" comes from the days when the ice was the main method of cooling capacity. Each pound 32F ice absorbs 144 BTU latent heat of fusion, as it melts in 32F water. In other words, each pound of ice is able to provide 144 BTU cooling capacity, as it melts in water. Tons of cooling capacity is equivalent to the amount of heat required to melt 1 ton of ice in 24-hour period. Tons of cooling load is the rate at which heat flows in space, when it melts 1 ton of ice in one day.
And here's why. We talked every pound 32F ice absorbs 144 Btuh in the heat of melting. Because ton contains 2,000 pounds, only 288,000 BTU per day (12,000 BTU / h) is the amount of heat needed to melt the ice. Ton cooling capacity/load, therefore, is defined as 12,000 Btuh.
You have to remember this fact and be able to use: 1 Tonne = 12,000 Btuh (or load power)..
|
Refrigeration 
