How to calculate heating and cooling loads
Calculation of heat convection is different from adaptation (Load). In many ways, we will begin by explaining the method of calculation of thermal load of heating and then we will explain the thermal load of cooling.
The Method of calculation of thermal load of heating:
The amount of heat required for heating is carried out by the thermal loss of the studied place, due to the thermal influence of walls, windows, surface, ground, doors and thermal loss due to leakage of air,It differs from the thermal load for conditioning in the summer so that we neglect the thermal load of people, machinery and lighting.
Basic data for calculation of the thermal load
- Total building plan and trends
- Floor sheds main, wall, windows and doorsdimensions
- A construction section and information on building materials, window materials and doors
- Choose interior and exterior design temperature for heated premises
- Calculate heat transfer coefficient for all heat exchangers, doors and windows
- Calculation of the surface area through which the exchange takes place
Choosing the internal temperature
The internal temperature is selected according to the following:
- Use of construction: It is the type of activity or work practiced by people in the construction, the more stressful the work the lower the temperature required.
- Age of persons: The temperature that achieves the thermal comfort of the elderly is different from the young
- Level of well-being of the building: the higher it is the higher the internal temperature rose
- Economic aspect: It is the most important factor and aims to reduce foundation and operational cost. We have chosen for the project the internal temperature of rooms 20C, although the thermal conditions for the comfort of people require the choice of internal temperature 22C for summer or winter to take into account not to cause a thermal shock to people coming from outside the building to take into account their physical health.
Selecting external design temperature
The external design temperature is related to the geographic location of the place. It is not necessary to choose the lowest temperature recorded in the area. The external design temperature can be higher by 8 degrees. The thermal capacity of the building here plays an important role, On the sharp drop that can occur between periods often occurs at night.
Calculation of total heat transfer coefficient (U)
The room is usually composed of several walls and ceilings, in addition to windows and doors,to calculate the total heat transfer coefficient, the thermal conductivity coefficient and the thickness of each of the previous elements should be defined in addition to the heat transfer factor for the internal and external surfaces.
The total heat transfer coefficient is given in the following relation:
U= 1 / (Ri + ∑ li / λi + Ro)
Ro = 1/ αois: Thermal resistance factor of the external surface
Ri = 1/ αi is:Thermal resistance factor of the internal surface
L =Surface thickness
λ =Thermal conductivity of the surface
The value of the thermal resistance factor of the internal surface is related to the direction of thermal flow and also to the quality of the surface studied.