Sensible Heat Ratio - SHR
The ratio Sensible Heat (or Cooling) Load to 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 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
