Sensible Heat Factor (SHF)

It is defined as the ratio of sensible to total heat transfer rate (Q_t), i.e.,

SHF = Q_s/ Q_t = Q_s/(Q_s + Q₁)

From the above equation, we can observe that a SHF of 1.0 corresponds to no latent heat transfer and a SHF of 0 corresponds to no sensible heat transfer. A SHF of 0.75−0.80 is quite common in air conditioning systems in a normal dry climate. A lower value of SHF, say 0.6, implies a high latent heat load such as that occurs in a humid climate.

The temperature, T_s, is the effective surface temperature of the cooling coil and is known as apparatus dew point (ADP) temperature. In an ideal situation, when all the air comes in perfect contact with the cooling coil surface, then the exit temperature of air will be same as ADP of the coil. However, in actual case the exit temperature of air will always be greater than the ADP temperature due to boundary layer development as air flows over the cooling coil surface and also due to temperature variation along the fins, etc. Hence, we can define a by-pass factor (BPF) as—it can be easily seen that, higher the BPF larger will be the difference between air outlet temperature and the cooling coil temperature. When BPF is 1.0, all the air by-passes the coil and there will not be any cooling or de-humidification.

where T_s is surface temperature of cooling coil; T_a is inlet air temperature; and T_c is outlet air temperature.