Domestic heating systems with a heat exchanger are generally assessed for efficiency by the ratio of primary energy input delivered energy output. In practice, performance depends on all the components in the heat delivery system and on their matching. In the air heating system addressed here, the components include: the gas burning air heater, supply ducts, return ducts, heat recovery system, controls, fans, filters and pumps. This paper describes experiments conducted on a test house in Bath during the years 1991 to 1993.
A new miniature mechanical ventilation system with both supply and extract air and an air-to-air heat exchanger has been developed in Great Britain and Denmark. The system which is intented to ventilate a single room has the dimensions of a shoe box and can be placed/installed on the inside wall in an existing air vent. The system can operate with two air flows, 40 or 70 m³/h. At the low speed the noise is insignificant, intended to be "not disturbingN in sleeping rooms.
This paper investigates quantitatively the energy conservation achieved by balanced ventilation with heat recovery and upstream ground heat exchanger. The investigations were conducted on an occupied single-family house equipped with such a balanced ventilation system. The heat recovery unit of this system consists of a plate-type heatexchanger with a downstream small air-to-air heat pump. In addition this house is equipped with a ground heat exchanger.
In well insulated buildings the ventilation heat is sometimes higher than the heat losses by transmission. For a air change rate of 0,8 per hour the specific heat flux must be calculated with 25 w/m², so heat recovery can save some energy. In all considerations the saving in the heating system must be compared with the additional energy for the fans, because this energy is of a higher quality. To optimize the heat recovery system, the different designs of the heat exchanger, the annual running hours and the annual hours for heat recovery must be taken into account.
A cross-flow polymer membrane enthalpy exchanger has been designed which provides both heat recovery and moisture dissipation in the ventilation of living spaces. The exchanger is of benefit in providing fresh air during both cooling and heating seasons with minimum loss of energy. A prototype of the enthalpy exchanger has been constructed and tested. The air leakage of the equipment has been found to be negligible; that is, the two air streams are indeed non-mixing.
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