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# 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

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## Citation

• The Engineering ToolBox (2004). Sensible Heat Ratio - SHR. [online] Available at: https://www.engineeringtoolbox.com/shr-sensible-heat-ratio-d_700.html [Accessed Day Month Year].

Modify the access date according your visit.

6.3.17

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