Specific heat

Each substance has its own unique specific heat. As can be seen from this chart, they vary widely. Substances with low numbers are the most easily heated. That is, they take a little heat to raise the temperature. For example, 1 pound of mercury (liquid metal)requires the addition of only 0.03 BTU to its temperature increases by 1F. note as aluminum, iron, copper and brass all have low specific heat. This means that they transfer heat easily. Cost and durability are reasonable, making them suitable materials of which do such things as heat exchangers, water heaters, refrigerant coils, furnaces, heat exchangers, boiler tubes.

These substances with high numbers require more heat. Water, for example, must absorb 1 full BTU of heat increase 1 1 poundF., Which is about 33 times more heat than is needed to raise the temperature of 1 pound of mercury for the same amount.

Looking at this concept in a slightly different way, in the right column of the table shows how much the temperature of 1 pound each substance would grow, if 1 BTU were added to it. This number does not heat capacity. It is shown, give practical understanding of the differences between the substances.

Heat capacities depends not only on the substance, but also from one state of matter in another state. Liquid water (1.00), for example, specific heat, twice the ice (0.50), which is a solid water. In other words, it will take twice BTU heat to raise 1 pound of water from 50 51 F, as it will raise 1 pound of ice from 20 to 21 F.

Specific heat can be calculated; in doing so, we can predict the number of explicit heat required to raise or lower the temperature of the substance a certain amount. The formula for calculating the amount of heat shown here. When we previously discussed, heating 1 pound of water from 32to 212 FF we used this formula without mentioning it. In this case, it works as follows:

Qs = Sp x W (AT) Q = 1.00 x 1.0 x (212F - 32F)

180 BTU heat must be transferred to the water in order to raise its temperature 32to 212 FF. BTU can be used for measurement of latent heat, as well as sensible heat. If we still warm pound of water by 212F, it starts to boil. As boils, its status changes at a constant temperature. Concealed heating began, and BTU added as each bubble steam (water in a gaseous state) is formed.

If we heat the water long enough liquid boils completely off. The amount of heat needed for this purpose is called the latent heat of vaporization. For water, it is 970 BTU per pound. Water seems to be fading, but actually present in a different form (in the form of gas) in the air. The heat absorbed from the burner now in the air and will remain there until it is removed by the cooling unit.

The heat required to change the state of a substance from solid to liquid is called the latent heat of fusion. As each substance has a latent heat of vaporization, specific heat of melting. The latent heat of melting water 144 BTU/lb. The latent heat for the transmission of any th position (BTU) can be calculated by multiplying its latent heat of fusion weight (in pounds) substances. If the substance is the transition from liquid to solid, heat must be removed from it. If it changes from solid to liquid, heat must be added to it.

As sensible heat, the amount of heat required to change water into vapor changes in the quantity proportional to the number of pounds of water. If he takes 970 BTU change 1 pound of water to steam, it will take 1940 BTU (2 lb (2 x 970). You can see that the amount of fluid exerts great influence on the amount of heat needed to boil water completely away. In other words, the volume of water has a great influence on how much the heat, the water can absorb become a gas.

This principle holds true when the liquid refrigerant inside the pipe cooling coil. More pounds of refrigerant circulates, the greater the capacity of the coils must absorb heat from the air. More power achieved by providing large coils and pump more refrigerant through them and more air over them.