DEVICE FOR HEAT TRANSFER FROM CHIPPINGS WHEN STORAGE IN HEAPS

Abstract

Introduction. Woodprocessing enterprises store chippings and other particulate wood-base materials at the unsheltered storage area in the heaps. Serious shortcoming of the mode of storage is spontaneous heating of chippings up to smoulder temperature  and its spontaneous ignition caused by vital activity of microorganisms. As a result of  smoldering,  cellulose content is decreased and timber chemical composition is changed. It  leads to permanent losses of vast number of chippings and provokes fire hazardous situation. Chipping is heated in the center of a heap most of all, accumulating heat. Thus, it is obligatory to deflect the heat and  lower the temperature of chippings. It is possible to solve the problem with the help of system of heat-removing elements, made on the basis of  heat pipes. The goal of the research is to study a test model of a device for heat transfer from chippings when storage in heaps. Tasks in hand is to develop and produce a test model of heat pipe, and to experimentally study  pipe temperature head. Research technique. The test model of heat pipe made of stainless steel 08Х13 (2,5 mm width and 50 mm diameter) was elaborated and produced. Body of pipe consists of cylindrical  and conical portions and it includes valve cover. The valve is meant for pipe filling with low boiling liquid. Pipe capacity is 2,65 l. Acetone with 56^○C boiling temperature was used as heat-transfer material. Surrounding air temperature (Т_sur.air   ) was 16^○С. The plan of experiment included two variable factors: temperature of heated medium Т_{heated medium.} , ^оС; and volume of heat carrier V_{heat carrier volume}, l. Pipe temperature in the evaporation zone Т _evaporation ^○С and Т_condensation^○С in  the condensation zone were measured in the course of the experiment, than temperature difference ∆Т, ^○С was defined. Mathematic simulation and results interpretation. Regression analysis made it possible to define mathematic dependence of temperature difference ∆Т, ^○С  on the temperature of heated medium Т_{heated medium}  , ^○С and heat carrier volume in the pipe V_{heat carrier volume} , l. Equation (2) allowed to define that pipe rejected heat more intensively when it was filled with  heat-transfer material  up to 0,23…0,30 of its inner volume. Conclusions. The obtained mathematical relation allows to define the necessary heat, which heat-transmitting element may transfer from the heap of chippings into the environment, consequently, it is  the device for  heat spreading system design .