دانلود رایگان مقاله انگلیسی تاثیر مبادل های حرارتی پنهان در طراحی مبدل حرارتی زمین هوا - نشریه الزویر

Abstract:

The work documents the design of Earth-Air Heat Exchangers based not only on sensible heat transfer, but also on latent heat exchanges. We compare the impact of the climate of Brazil and south of France on the relevance of such systems. The duct length is determined in order to obtain maximum underground heat exchanges. A time dependent model combined to actual weather data is developed to show when an underground heat exchanger becomes a good option in a tropical climate. The three-dimensional version of the model accounts for heat transfer in the soil and for heat and moisture transfer along the underground pipe. The comparison with a 1D model allows to propose a straightforward approach to assess the cooling/heating potential of different climatic regions.

5. Concluding

remarks Earth-Air heat exchangers are an old technique known since the Roman Empire around the Mediterranean Sea. Today, with the increasing concern in global warming and the objective of including renewable energy in the heating/cooling solutions for indoor comfort, EAHE experiences a renewed interest in several countries including Brazil. In this work we developed a model to account for latent and sensible heat exchanges between the buried pipe and the soil. By comparing the results to the climate of south of France, we look for the conditions when EAHE is an interesting solution. An example of tropical climate (Rio do Janeiro) was picked and the heat exchanges were envisaged in 2 extreme cases: considering sensible enthalpy only and adding latent heat exchanges when the pipe wall is wet. We show that the latent heat exchanges cancel the positive effect that the EAHE may have: Even though in summer the air is blown into the house at a lower temperature than the outdoor; the air is humidified to such an extent that the air conditioning system would have to spend more power to maintain indoor comfort.

The 3D modelling of conduction heat transfer through the soil showed almost no difference with the approach consisting in calculating the pipe wall temperature at its buried depth from an analytical soil temperature function. The next step of this work will consist in including to the present study the hydric state of the soil and modelling its impact on the overall heat transfer through the pipe.