SHR - STULZ answers

The Sensible Heat Ratio (SHR) reflects the ratio of the sensible (perceptible) heat load (Q_sensible) and the total heat load (sensible & latent).

Calculation example

A cooling system emits a total amount of heat of 20 KJ/kg to cool the cabin at atmospheric pressure from 35 °C to 26 °C. The air inside the cabin has an average heat of C_P of 1.050 KJ/kg.

Q_total = 13 KJ/kg

T_initial = 32 °C

T_final = 26 °C

C_P = 1.050 KJ/kg

The total heat load (Q_sensible) can then be calculated:

Q_Sensible = C_P (T_initial – T_final)

 Q_Sensible = 1.050 (35 – 26)

 Q_Sensible = 9.450

Then the SHR is calculated as follows:

SHR = Q_sensible / Q_total

SHR = 9.450 / 13

The SHR amounts to 0.726
 

An SHR lower than 1 means that due to dehumidification of the air, the air conditioning system in a data centre is less efficient than it should be. Typically, dehumidification in a DC is not necessary.