DYNAMIC MODELING OF MICRO-CLIMATE CONDITIONS OF A GREENHOUSE COUPLED WITH COAL FIRED HOT-AIR FURNACE

Abstract

ABSTRACT In this study, a thermal analysis of a greenhouse heated with a coal-fired furnace was done. A greenhouse in the Mediterranean basin of Turkey was modeled. Energy and mass balances were derived to estimate the inside air temperature, humidity ratio and soil surface temperature, and the coal consumption rate. A dynamic approach was taken into account to define the time-dependent changes of the parameters in the greenhouse during the coldest period of the region, January and February. The main heat loss of the greenhouse occurs through the wall, ceiling and ground by convection and conduction. This heat loss is 63% of the total daily heat gains of the greenhouse for the coldest day. Furnaces were designed to maintain the greenhouse inside temperature approximately at 15ºC and averagely 200 kg coal was consumed per day. The maximum coal consumption amount was 480 kg for the coldest day. A meteorological data based solar radiation model was used, including dry-bulb temperature, relative humidity, wind speed and cloud cover. The effect of the cloud cover on greenhouse heating was investigated. For the coldest day, rather the sunrise was at 07:00 am, the furnaces were fired up to 10:00 am because of low solar radiation at that cloudy sky condition period. During the daytime, solar energy storage in the soil led to an increase in soil temperature. Approximately 1.5ºC-2ºC temperature difference on the soil surface was computed before and after the daytime. Finally, thermal characteristics of the furnace such as flue gas temperature and flow rate, furnace wall temperature, required amount of air for the combustion process were determined.