# Sensible Heat Ratio - SHR

## Sensible Heat Ratio - SHR - is defined as the sensible heat or cooling load divided by the total heat or cooling load

The Sensible Heat Ratio - SHR - is used to describe the ratio of sensible heat load to total heat load and can be expressed as:

SHR = q_{s}/ q_{t}

=q) (1)_{s}/ (q_{s}+q_{l}

where

SHR = sensible heat ratio (ratio of sensible heat load to total heat load)

q_{s}= sensible heat load (kW, Btu/hr)

q_{t}= total heat load - sensible heat and latent heat (kW, Btu/hr)

q_{l}= latent heat load (kW, Btu/hr)

For an air flow *(1)* can be modified to:

SHR = c_{p}(t_{o}- t_{i}) / (h_{o}- h_{i}) (2)

where

c_{p}= specific heat air (1.005 kJ/kg^{o}C, 0.240 Btu/lb^{o}F)

t_{o}= outlet air temperature (^{o}C,^{o}F)

t_{i}= inlet air temperature (^{o}C,^{o}F)

h_{o}= outlet moist air enthalpy (kJ/kg, Btu/lb)

h_{i}= inlet moist air enthalpy (kJ/kg, Btu/lb)

### Example - SHR for a room

The inlet temperature to a room with some people is *20 ^{o}C*. The relative moisture of the inlet air is

*50%*. From the Mollier chart the enthalpy of the inlet air is

*37 kJ/kg*.

The outlet temperature is *26 ^{o}C* and the relative moisture of the outlet air is

*40%*. From the Mollier chart the enthalpy of the outlet air is

*47 kJ/kg*.

The Sensible Heat Ratio can be calculated as

*SHR = (1.005 kJ/kg^{o}C) ((26 ^{o}C) - (20 ^{o}C)) / ((47 kJ/kg) - (37 kJ/kg))*

* = 0.6*

*60%* of the load provided to the room heats the air (sensible load) and *40%* of the load provided humidifies the air (latent load).

### Example - SHR for a evaporator

If the SHR value for an evaporator is* 75% (0.75) - 75%* of the load cools the air (sensible load) and *25%* of the loads dehumidifies the air (latent load).

### General Design Values

- Auditoriums, Theaters - SHR : 0.65 - 0.75
- Apartments - SHR : 0.80 - 0.95
- Banks, Court Houses, Municipal Buildings - SHR : 0.75 - 0.90
- Churches - SHR : 0.65 - 0.75
- Dining Halls - SHR : 0.65 - 0.80
- Computer Rooms - SHR : 0.80 - 0.95
- Cocktail Lounges, Bars, Taverns, Clubhouses, Nightclubs - SHR : 0.65 - 0.80
- Jails - SHR : 0.80 - 0.95
- Hospital Patient Rooms, Nursing Home, Patient Rooms - SHR : 0.75 - 0.85
- Kitchens - SHR : 0.60 - 0.70
- Libraries, Museums - SHR : 0.80 - 0.90
- Malls, Shopping Centers - SHR : 0.65 - 0.85
- Medical/Dental Centers, Clinics and Offices - SHR : 0.75 - 0.85
- Motel and Hotel Public Areas - SHR : 0.75 - 0.90
- Motel and Hotel Guest Rooms - SHR : 0.80 - 0.95
- Police Stations, Fire Stations, Post Offices - SHR : 0.75 - 0.90
- Precision Manufacturing - SHR : 0.80 - 0.95
- Restaurants - SHR : 0.65 - 0.80
- Residences - SHR : 0.80 - 0.95
- Retail, Department Stores - SHR : 0.65 - 0.90
- Other Shops - SHR : 0.65 - 0.90
- School Classrooms - SHR : 0.65 - 0.80
- Supermarkets - SHR : 0.65 - 0.85