VENTILATION HEAT RECOVERY WITH COOLING
Required area of air outlet
Type of room or building
Office
Intake air is cooled down by circulating fluid
Meeting room Reception Auditorium
Restaurant/cafe Sports hall Classroom
The extracted heat is reused, for example hot tap water
HWT HP
Figure 2: An example of sustainable cooling with NVHRC
outdoor temperature is below freezing, the room will have a net heat demand, since there is an insufficient heat potential in the outlet air to heat up the room. Where the outside temperature is cool (5C to 10C) there may be more heat potential in the outlet air than is needed for heating the room, and the surplus heat can be used in other parts of the building. (See Figure 3.) The idea of using a heat pump to extract
Natural ventilation is considered to have many potential advantages over commercially used air conditioning, pictured below
heat from the outlet air is, of course, not new. Typically, mechanical exhaust and ductwork is used for ventilation; a heat exchanger placed in the discharge
Common room Kindergarten Bank
Bakery Dance hall Exhibition hall
Required area of air outlet per 100 sq m net floor area
0.2 1.0 0.4 1.0 1.0 0.4 0.6 0.2 0.5 0.4 0.9 0.3 0.1
Figure 3: Estimated required size of the air outlet for various building types
airstream, via a heat pump, transfers heat to the heating system. But in NVHRC, natural ventilation is used, eliminating the electricity consumption for mechanical exhaust.
Sustainable cooling If the room requires cooling, the cold circulating fluid can be directed to an air intake unit. The fluid will cool down the intake air, and the heat extracted by the heat pump from the circulating fluid can be transferred to meet coincident heating system requirements. The heat will usually
44
CIBSE Journal July 2011
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