Sensible Heat Ratio - SHR
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 s / (q s + q l ) (1)
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 = cp (t o - t i ) / (h o - h i ) (2)
where
cp = specific heat air (1.005 kJ/kg oC, 0.240 Btu/lb oF)
t o = outlet air temperature ( oC, oF)
t i = inlet air temperature ( oC, oF)
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 oC . 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 oC 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 oC ) (( 26 oC ) - ( 20 oC ) ) / (( 47 kJ/kg ) - (3 7 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
Related Topics
• Air Conditioning Systems
Design of Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort.
• Air Psychrometrics
Moist and humid air calculations. Psychrometric charts and Mollier diagrams. Air-condition systems temperatures, absolute and relative humidities and moisture content in air.
Related Documents
Cooling and Heating Equations
Latent and sensible cooling and heating equations - imperial units.
Cooling Load - Latent and Sensible Heat
Latent and sensible cooling loads to consider when designing HVAC systems.
Great Sensible Heat Factor - GSHF
The Great Sensible Heat Factor is the ratio sensible to total heat in a cooling coil.
Heat Index
Equivalent heat index vs. air temperature and relative humidity - in degrees Fahrenheit and Celsius.
Heat Recovery Efficiency
Classification of heat recovery efficiencies - temperature efficiency, moisture efficiency and enthalpy efficiency - online heat exchanger efficiency calculator.
HVAC Abbreviations
Commonly used HVAC abbreviations.
Indoor Relative Humidity vs. Outdoor Relative Humidity and Temperature
Recommended indoor relative humidity vs. outdoor relative humidity and temperature.
Latent Heat Flow
Latent heat is the heat when supplied to or removed from air results in a change in moisture content - the temperature of the air is not changed.
Room Sensible Heat Factor - RSHF
Room Sensible Heat Factor - RSHF - is defined as the sensible heat load divided by the total heat load in a room
Sensible Heat Flow
Sensible heat is dry heat causing change in temperature but not in moisture content