Research Of The Influence Of On-line Rubber Ball Cleaning Device On Chiller Performance

In China,chillers are widely used,but fouling in condenser is a prevailing problem,which results in the reduction of the thermal performance and the increase of condensing temperature in condenser.Thus,the compressor power consumption is increased and the energy efficiency of chillers is decreased.It will play a positive role in building energy saving to remove fouling of condensers timely which maintain high heat transfer efficiency for condensers,and improve COP of electric water chiller.This paper compared and analyzed the test data of chillers with and without on-line rubber ball cleaning device,including fouling resistance,COP,temperature difference.The results showed that on-line rubber ball cleaning device had good effect in removing fouling.In this paper,the numerical simulation with Fluent software was used to verify the heat transfer enhancement of on-line rubber ball cleaning device.Then the heat transfer enhancement of the device is evaluated by field synergy principle and PEC(Performance Evaluation Criteria)principle.On the basis of test and simulation,the economics was analyzed,and optimal cleaning cycle was decided.Experimental results showed that,comparing to the chiller without rubber ball cleaning device,average fouling resistance of condenser was reduced by 58.66%,average COP was improved by 8.46%,and the temperature difference was decreased significantly.According to the test data,COP of the chillers was improved 6.93% ~8.46% by using on-line cleaning device,which had a remarkable energy-saving effect.According to the simulation results of Fluent software,the heat exchange capacity between tube wall and cooling water was increased due to the rubber ball flowing in the condenser tubes.Only considering from the heat exchange perspective,the heat transfer enhancement of the device is evaluated by field synergy principle.Comparing to the chiller without rubber ball cleaning device,the angle between velocity and temperature gradient in tube reduced 7° ~13° which indicated that rubber ball enhanced heat transfer.Taking PEC as an overall evaluation criteria,PEC was in the range of 1.05~1.12 by calculation,slightly larger than1.In terms of heat transfer and transmission energy consumption,although the heat transfer can be enhanced by rubber ball,the effect was limited.In this paper,taking minimum cost per unit time as the objective function,optimal cleaning cycle calculation model was established.Through optimization analysis,the best cleaning cycle was 36 h,in which the cleaning interval is 28 h and cleaning work lasted 8h.In this operational situation,minimum operating cost was 194.4 yuan per hour which was decreased by 3.76% comparing to the continuous cleaning mode.The initial investment of on-line rubber ball cleaning device was about 100,000 yuan.It can save energy cost of 41,840.64 yuan every year,so the dynamic payout period of rubber ball cleaning device is 2.60 years.It can be concluded that the energy saving effect and economic benefit of the device benefit is very remarkable.