Introduction. Efficiency of application of the pump heat-insulating cover, filled by water, in conditions of self-heating for decreasing the ice-forming inside fire hoses is examined. Experimental technique. The object under research was the centrifugal pump PN-40UV installed on the fire extinguishing water tanker ATs-3,2-40(433114) which accrued operating time is 186 hours with resource of the special unit equal to 1100 hours. According to the patent of the Russian Federation № 68324 the demountable cover consist of two heat-insulating layers of half-woolen blankets and one heat-reflecting layer of metalized half-linen fabric with layers of air between them. The temperature of air and the initial temperature of water in the pump was accordingly (5±1) and (20±1) °C. To register the temperature it was used the electronic potentiometer EPP-09. Chromel copel thermocouples were placed along the axis of the pump inlet duct and in its collector. The average temperature of the system was defined as arithmetic mean of indications of these devices. The frequency of pump impeller rotation and torque data was measured to determine the shut-off capacity of the pump. Results of research. The calculating model which adequately describes the process and can be used, for example, in determination of time of water self-heating up to the set temperature depending on the ambient temperature and shut-off capacity of the pump is received. Exergetic efficiency of preliminary self-heating of water in the pump to ensure an idle running power rates about 14,0 and 23,5 kW (and frequency of rotation of the pump impeller shaft—1900 and 2700 rpm accordingly) is calculated. It is established that efficiency of the process of preliminary self-heating of water by the pump, before feeding into the main hose line, is low and fluctuate in the range of 3,3...7,5 %. The part of heat exergy removed by the pump surface into the environment is 0. 027...0,126 %. The maximal part of exergy loss during conversion of work into heat is 0,94...0,88 %. Besides, about 1,74...3,92 % of heat is spent on heating of the pump elements. From this volume of heat more than 81 % absorbs by pump case, more than 7 % by pump impeller and more than 10 % totally by spindles of valves and oil bath. Conclusions. 1. The examined construction of heat insulation of the pump PN-40UV is slightly speed up preliminary self-heating of the water in special unit, before feeding into the main hose line, as exergy heat losses removed by external surfaces of the fire pump into the environment are insignificant. However, during the further operation of the pump at a fire the presence of heat insulation will allow to provide the intensive attendant heating of extinguishing liquid that is necessary for its feed with required strength during the whole period of extinguishing. 2. The part of exergy of useful work of the special unit spent for self-heating of the water increases with the warming up time and rising of its temperature. 3. Use of heat-insulating cover of internal surfaces of the pump case parts will allow redirecting the certain part of heat to intensive self-heating of water in the special unit. 4. Application of exergetic method of analysis provide a way of system and complex estimation of the perfection degree of thermodynamic processes in systems of fire-fighting vehicles as it gives thorough representation about character of use of energy resources and about specific weight of losses in its various elements.
|Translated title of the contribution||EXERGY ASSESSMENT OF HEAT EFFICIENCY FOR SELF-HEATING OF WATER BY MEANS OF FIRE ENGINE PUMP|
|Number of pages||13|
|Publication status||Published - 2013|
- 81.00.00 GENERAL AND COMPLEX PROBLEMS OF TECHNICAL AND APPLIED SCIENCES AND BRANCHES OF THE NATIONAL ECONOMY
Level of Research Output
- VAK List