(J. of the Society of Agricultural Structures, Japan, 36(1), 37-45, 2006)

Analysis of Greenhouse Heat-releasing Mechanisms in Snowy and Cold Areas

Shintaroh OHASHI and Kazuhiro NAKANO

Summary

In researching the heat-releasing mechanisms of greenhouses in snowy and cold areas, the heat characteristics, such as the heat loss coefficient, over-all heat transfer coefficient and ventilation heat transfer coefficient, can be very effective factors. However, they are subject to the changes of covering methods, heating methods and operating conditions and so on. These characteristics must be minutely calculated in pursuit of enhancing energy-saving capacities or reducing the heating cost. In this paper, the heat characteristics of the greenhouse are calculated based on the results obtained from the measured values of meteorological parameters, inner and outer wall temperatures and so on. The present state and the feature of the temperature management of the greenhouse in snowy and cold areas were discussed using above heat characteristics. As a result, the following has become clear:

(1) The proportion of the over-all heat transfer, ventilation heat transfer, and soil heat transfer to total heating load was 46%, 46%, and 8%, respectively.

(2) The heat loss coefficient of the greenhouse was 8.18kJ･h-1･m-2･K-1，over-all heat transfer coefficient was 8.05kJ･h-1･m-2･K-1 and ventilation heat transfer coefficient was 0.13kJ･h-1･m-2･K-1.

(3) It was proved that the greenhouse used in this study was an airtight one.

(4) In nighttime, the actual amount of heat supply in greenhouse was almost the same as the value calculated from the heating load using degree-hour method. However, the value of the amount of heat supply in daytime was up to 3.6 times as much as the calculated value.

(5) The features of the temperature management or issues of enhancing energy-saving cultivation were pointed out by analyzing the data measured in the greenhouse in snowy and cold areas.



Return