Shr Sensible Heat Ratio

Overview

Engineering reference data for Shr Sensible Heat Ratio in thermodynamics.

Key Formulas

First Law

$\Delta U = Q - W$

Energy is conserved — heat added minus work done.

Ideal Gas Law

$PV = nRT$

Relates pressure, volume, and temperature of an ideal gas.

Heat Transfer

$Q = mc\Delta T$

Sensible heat transfer.

Carnot Efficiency

$\eta = 1 - T_C/T_H$

Maximum efficiency between two temperatures.

Variables

Symbol	Description	Unit
$U$	Internal energy	J
$Q$	Heat	J
$W$	Work	J
$P$	Pressure	Pa
$V$	Volume	m³
$T$	Temperature	K

Formulas and Examples

The core relationships for calculating the Sensible Heat Ratio (SHR) are:

General Definition:

$$SHR = \frac{q_s}{q_t} = \frac{q_s}{q_s + q_l}$$

For an Air Flow Process:

$$SHR = \frac{c_p (t_o - t_i)}{h_o - h_i}$$

Example Calculation: For a room with inlet air at 20°C (enthalpy 37 kJ/kg) and outlet air at 26°C (enthalpy 47 kJ/kg):

$$SHR = \frac{1.005 \, \text{kJ/kg·°C} \times (26°C - 20°C)}{47 \, \text{kJ/kg} - 37 \, \text{kJ/kg}} = 0.6$$

This means 60% of the load is sensible (heating the air) and 40% is latent (humidifying the air).

Design Values by Application

Typical SHR values vary significantly based on the type of space and its associated moisture loads.

References

• Original Source