HEAT TRANSFORMATION IN THE PLANT FOR INTEGRATED ENERGY SUPPLY BY LITHIUM BROMIDE ABSORPTION MACHINE

The efficiency of waste heat transformation from gas engines in the plant forintegratedenergysupply by lithium bromideabsorption refrigerating machine was analyzed. Such gas engines are equipped with heat exchangers for producing hot water from the engine recoverable heat. The waste heat from gas engine jacket and lubricant oil cooling water, scavenge gas-air mixture and exhaust gas are used to produce hot water with the temperature of about 90 °С as heating source for absorption chiller. The analysis was made for trigeneration plant on the base of cogeneration reciprocating gas engine modules JMS 420 GE Jenbacher. This trigeneration plant was designed for combined energy supply of the factory "Sandora"?"PepsiCо Ukraine" (Nikolaev, Ukraine). The trigeneration plant, equipped with two cogeneration JMS 420 GE Jenbachergas engine modules and a single-stage absorption chiller, has been designed and assembled by "Sinapse"?"GE Energy" (Kiev) and "Khladotechnika" (Nikolaev). The absorption chiller produces chilled water for technology process cooling and conditioning of engine room intake air. The significantheat losses were revealed caused by the cogeneration gas engine modules and the lithium bromideabsorption chiller temperature regime performance discrepancy. In its turn it was caused by the increased temperature of return water from the single-stage absorption chiller of about 75 °С to the parts of the gas engine to be cooled. But in respect of the condition of engine reliable maintenance at the appropriate thermal rate the temperature of the return cooled water entering the engine cogeneration system is limited to the design value not exceeding 70 °С. If it excess, a surplus heath of return water is rejected to the atmosphere by the cooling tower. Return of excess heat to a single-stage absorption chiller is impossible because of its temperature of 75…78 °С lowered rather design temperature of the supply hot water for a single-stage absorption chiller of 90…95 °С. Fall of temperature of the supply hot water to a single-stage absorption refrigerating machine would cause considerable dropping the efficiency of transforming a gas engine recoverable heat into a cold ? decrease in coefficient of performance (COP) from nominal (design) value of about 0.7 to 0.5 and lower. The results of water temperature and flow measuring showed the heat losses of 30...40 % of the heat transformed by absorption chiller into a cold.There were proposed an improved two-stream system of return water flow to the cogeneration gas engine modules that reduces the heat losses compared with traditional one-stream variant. In the two-stream system the watermass flow through cogeneration gas engine modules and absorption chiller is increased up to about 150 % compared with the base variant and the return cooled waterflow from the absorption chiller is divided into two streams.With this the temperature of the supply hot water for the absorption chiller, leaving the cogeneration gas engine modules, and the temperature of return cooled water from the absorption chiller is lowered as compared with the base one-stream system. Oneofthereturn water stream ? ofthesamemassflowasinthebasevariant but at the lowered temperature?iscooled down to the required temperature of 70 °С as in thebasevariantand directed to the gas engine nodes those need cooling. The other (addition) return water stream of the50 % massflowand of increased temperature higher than 70 °С is delivered directly to the gas engine exhaust gas recovering boiler (economizer) by-passing the gas engine cooling nodes. It was shown that the two-stream system of return water flow to the cogeneration gas engine modules increases cooling capacity by approximately 25 % compared with traditional one-stream variant due to reducing the heat losses during transformation of gas engine waste heat into a cold.