heat recovery

What has heat recovery done for the cause or energy efficiency? If some manufacturers or heat recovery equipment are to be believed, the savings in ventilation costs are "quite staggering".

In order to explain the effect of heat recovery on a passive ventilation system using stack effect, and to show the factors and conditions that the heat-recovery system can be installed in a passive ventilation system, the following investigations are made. The characteristics of the airflow in houses using the passive ventilation with the heat recovery units were investigated from scale model experiments and numerical experiments. And the effect of energy saving by the heat recovery system was investigated from numerical experiments using the standard weather data of cities in Japan.

The study was to test five units used in single house mechanical ventilation systems with heat recovery. Tests were made according to CEN project prepared by CEN TC 156/WG2/AH7 including air tightness, pressure-airflow's curves and temperature ratios. A full test on frost and condensation was also realised on one unit to determine the influence of these parameters on performances. Test results, influence of wet or dry conditions and main conclusions for using these results in dimensioning, will be given.

Two energy-efficient single-family houses (known as ESPI houses) with competitive overallcosts were set up during the study in Finland. The consumption of energy for room heating inESPI houses was reduced to a half at the construction stage, by employing simple solutionswhich can be used by every builder. The level of thermal insulation of the houses wasimproved remarkably. The houses were equipped with a controlled ventilation system and anefficient exhaust air heat recovery unit. One of the houses was oil heated and the other waselectrically heated.

In the EU Joule project Nat Vent one of the work packages was dealing with controlled air flow inlets. During the last conference in Greece and overview was presented on availability, performances and application of controlled air flow inlets. At the presented poster an interactive IAQ computer tool was demonstrated. This tool has been improved and is now available. Some participating countries in the Nat Vent project have carried out special tests with the NatVent IAQ tool. The NatVent participants were asked to design a natural ventilation system according to their national requirements.

Measured contaminant and heat removal effectiveness data are presented and compared for a 3: 1 scale model room, which represents a smoking room, lounge, or bar with a two dimensional airflow pattern. In the experiments, heat and tracer gases were introduced simultaneously from a source to simulate a prototype smoking room. High-side-wall and displacement ventilation schemes were investigated, and the latter employed two different types of ceiling diffuser, low velocity slot and low-velocity grille.

The large heat loss from Passive-stack ventilation (PSV) systems quite often makes natural ventilation systems unattractive and it is therefore desirable to implement heat recovery in PSV stacks. As the stackpressure is usually about a few Pascal, it is crucial that the heat recoveryunit used in a PSV system produces even lower pressure loss, which is extremely difficult to achieve with the conventional plate heat exchangers. This work is concerned with an a low pressure-loss heat recovery device based on heat pipes.

This paper will describe a proposal to upgrade a thermally sub-standard multi-storey housing block (Type T84), where height and climatic exposure are significant, to demonstrate the effectiveness of passive, active and hybrid solar techniques to minimise space and water heating loads while enhancing the quality of air in both shared and private spaces.