Abstract
In the context of this article, a caloric method for measuring the performance of alternating home ventilation devices (push-pull units) is presented. The simple and robust method provides both reliable and reproducible characteristic values. Based on this method, a test bench was developed and built. With this test bench the characteristic values (volume flow, heat recovery rate, temperature change rate) of series products can be measured. The aim of the investigation is the determination and evaluation of the possible parameters influencing the measurement. For this purpose, the parameters are illustrated on the basis of measured values from a defined test standard, consisting of a fan and electrical heating in a housing (so-called golden sample), as well as a pair of push-pull devices. As a result, suggestions for improvements to the previous procedure as well as approaches for further development are shown.
Highlights
An unbalanced mass flow between both ventilation units leads to a pressure difference between the test bench chamber and the environment
Whilst all methods provide reliable efficiency ratios and are suitable for the measurement of ventilation units with changing mass flow direction, the method with the lowest uncertainty is the caloric measurement method according to the power propagation law
The influence of ambient conditions on volume flows below 25 % of the nominal volume flow should be investigated in further projects
Summary
Due to the increasing demands on energy efficiency in the construction sector, tightness and thermal insulation are constantly increasing. Alternating home ventilation devices (push-pull units) have advantages due to their working principle and easy installation procedure at this field. Consisting on one fan and a sensitive heat accumulator, the direction of the air mass flow is changed by reversing the fans direction of rotation over time τ. Where B is the mode of operation (B = 1 air from ambient into the room, B = −1 from room to ambient), ṁ as mass flow and T as temperature with ETH as extraction air, EHH as exhaust air, SUP as supply air and ODA as outdoor air. The air temperature at the indoor side of the unit is denoted by i and at the outdoor side by a. The temperature at the outdoor side of the unit is decreased by this energy transfer. The energy stored within the accumulator is transferred to the outdoor air at B = 1
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