Sharp JX-9400 Informações Técnicas descarregar pdf (Página 106)

can be transferred from the warm side to the other. The heat recovery eﬃcie ncy

of these exchangers ranges from 60 to 80 per cent, depending on the type and

size. A variant of this exchanger is the heat pipe exchanger, in which heat pipes

are used to transport heat from warm to cold air. The air leakage between both

sides of such heat exchangers should be zero.

Rotating heat exchangers

Rotating heat exchangers are used in larger systems (see Figure 5.5). A disc

with a porous structure (honeycomb, corrugated metallic foils) allowing the

air to ﬂow easil y through it, is placed so as to have half of its area in the exhaust

duct, and the other half in the supply duct. This disc rotates slowly and is

heated in the warmer air, where air moisture may also condense on the surfac e

of the porous structure. It is then cool ed in colder, dryer air, also evaporating

here the condensed water. This way, sensible and latent heat contained in warm

air is given to cold air, and the heat recovery eﬃciency may reach 90 per cent. A

gasket and a purging sector limit contamination from exhaust air to fresh air,

without eliminating it completely (see Chapter 6, ‘Contaminant transport in

rotating heat exchangers’).

A small leakage can be accepted in a rotating heat exchanger, resulting in a

recirculation rate of less than 4 per cent. Reduced leakage is achieved by care-

fully installing the rotating heat exchanger, and by balancing the air pressure

between both sides of the exchanger. To achieve this, supply and exhaust

fans should not be on the same side of the heat exchanger (see Figure 5.6).

Figure 5.5 Top half of a rotating heat exchanger

Measurements and Measures Related to Energy Eﬃciency in Ventilation 85

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