OPTIMIZATION OF HEAT PUMPS IN DRYERS

The rapid rise in energy prices in the world makes the problem of energy saving relevant for today. Drying of materials is one of the most energy-intensive heat-technological processes. Despite the high heat consumption for drying processes, the quality of the resulting material may not meet modern requirements, and the specific energy consumption will be too high. Therefore, consideration of new means and devices for drying materials using heat pumps is promising. 
The efficiency of the dryer depends on the degree of air recirculation. In dryers, complete recirculation of exhaust gases is impossible, since an increase in the moisture content of the air significantly reduces its drying capacity. But the heat pump can be effectively used as a means of removing moisture from the exhaust gases of the dryers, while it is possible to increase the proportion of their recirculation. 
The aim of the study is to determine the optimal value of the percentage of recirculation of the treated exhaust gases from the dryer, at which the greatest energy savings are achieved. 
The installation of a heat pump downstream of the dryer on the flue gas side effects both the humidity and temperature conditions by recirculating some of the flue gases treated in the heat pump to the dryer inlet. As the results of the study showed, the use of a heat pump to dry the exhaust wet gas and return it to the cycle makes it possible to increase the efficiency of the dryer, but energy is wasted to drive the heat pump compressor. In accordance with this, the consumption of primary fuel is also reduced to obtain the required amount of thermal energy for heating. 
The developed method makes it possible to determine the optimal proportion of exhaust air recirculation in dryers in order to achieve the greatest savings in primary fuel compared to conventional recirculation.