Great Sensible Heat Factor - GSHF

A cooling coil should have the capacity to handle the heat load generated in the room in addition the capacity to cool down the fresh make up air. The Great Sensible Factor is independent of the total air flow and can be expressed as

GSHF = (Q_s + m_f c_p (t_f - t_r)) / (Q_t + m_f (h_f - h_r))                                  (1)

where

GSHF = Great Sensible Heat Factor

Q_s = sensible heat generated in the room (kW)

m_f = fresh air mass flow (make up air) (kg/s)

c_p = specific heat of air (kg/kg^oC)

t_f = temperature in fresh air (^oC)

t_r = temperature in room air (^oC)

Q_t = total heat generated in the room (kW)

h_f = specific enthalpy of fresh air (kJ/kg^oC)

h_r = specific enthalpy of air in the room (kJ/kg^oC)

Example - Great Sensible Heat Factor - GSHF

The sensible heat generation in a room is 4 kW and the latent heat generated is 1.4 kW. The room is cooled with an air flow of 1000 kg/h.

The fresh (out door) air temperature is 28 ^oC with a specific enthalpy of 60 kJ/kg and a humidity ratio of 12.7 g/kg.

The room temperature is 22 ^oC with a specific enthalpy of 45 kJ/kg and a specific humidity of 9.1 g/kg.

The Great Sensible Heat Factor can be calculated like

GSHF = ((4000 W) + (1000 kg/h)(1/3600 s/h)(1000 J/kg^oC)(28 ^oC - 22 ^oC)) / ((4000 W + 1400 W) + (1000 kg/h)(1/3600 s/h)(60000 J/kg - 45000 J/kg))

= 0.59