Heat Control and Cooling a Home
Heat control in our homes provides comfort levels for all seasons. The familiar term “cold” refers to the absence of heat. At absolute “0” there is a complete absence of heat and atomic activity ceases. Heat, or energy, is produced by atomic activity. As a result of this scientific principle, heat will always flow to the cooler area or object and stimulate atomic energy release in the colder subject. The faster moving atoms give up some of their energy to slower moving atoms. This causes the faster atoms to slow down a little and the slower ones move a little faster. In order to discuss heat and its many aspects, an operational definition is needed. There are three units commonly used; the calorie, the kilocalorie, and the British thermal unit (BTU). The BTU is the unit most commonly heard in home cooling and heating discussions. One BTU equals 252 calories, which in turn equals 0.252 kilocalorie. The process of heating a house involves introduction of heat into the structure and distribution to the areas where needed. Cooling of the same structure involves removing heat. Both processes are conducted in an outside environment which usually opposes the process being performed. When it is cold outside, you are trying to heat the inside of the structure. When it is hot outside, you are trying to cool the inside. These environments detract or encumber the process being conducted. Leakages from and into the structure complicate the processes and increase the capacities of the needed systems.
Cold air is heavier than warm air, and warm air rises as it is displaced by the cooler air existing at or near ceiling level. Therefore, the heat flow in a house is from the heated, lower levels of the structure, upward toward the ceiling. As it lingers at the ceiling it will eventually cool and fall to the lower levels to absorb heat and repeat the heating and cooling air flow cycle. This principle accounts for the air circulation pattern in a heated structure. At some point this exchange of warm and cool air will reach a state of essentially equilibrium (average out) and give a sensation of uniform warmth, assuming a heating unit of adequate capacity. This principle also applies to the summer cooling requirement. Now the cool air must displace and remove the warmer air. However, the delivery system for the cool air will most likely require a greater capacity due to the heavier cool air. Based on this principle, it is possible that a single source can supply the heating and/or cooling requirement for a whole house. The system requirements are usually based on the cooling capacity requirement. These heating and cooling principles include conduction, radiation, and convection.