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Sensible Heat Ratio - SHR

The ratio Sensible Heat (or Cooling) Load to the Total Heat (or Cooling) Load.

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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 = c p (t o - t i ) / (h o - h i )                                              (2)

where

c p = specific heat air (1.005 kJ/kg oC, 0.240 Btu/lb o F)

t o = outlet air temperature ( oC, o F)

t i = inlet air temperature ( oC, 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 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
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Related Topics

  • Air Conditioning

    Air Conditioning systems - heating, cooling and dehumidification of indoor air for thermal comfort.
  • Air Psychrometrics

    Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.

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