Energy Savings through Retrofitting Waste Heat Recovery System on Bulk Milk Cooler

This study highlights about energy savings through retrofitting waste heat recovery system on bulk milk cooler. Various types of heat exchangers are being used for recovering waste heat in which tube in tube type are the most common. Bulk milk coolers are used to chill the milk from its harvest temperature of 350C to 40C to arrest the bacterial growth and maintain the quality of harvested milk. Milk chilling practices are energy intensive with low coefficient of performance (COP) of about 3.0. Increased energy cost concern encouraged an investigation of heat recovery from bulk milk cooler as one conservation alternative for reducing water heating cost in dairy industry. Heat dissipated to atmosphere through condenser is recovered to improve the energy efficiency of plant. The waste heat is utilized to heat the water which is used to clean the milk processing equipment’s thus saving thermal or electrical energy used to heat the water separately. Shell and coil type heat exchanger is designed and used to recover the waste heat during condensation process. Heat rejected in condensation process consists of superheat and latent heat of the refrigerant. In this work, attempt has been made to recover complete superheat along with part of latent heat which is a present research issue. Various types of heat exchangers are being used for recovering waste heat in which tube in tube type are the most common. The results show that complete superheat and 35% of latent heat is recovered. Heat recovery rate is measured for various mass flow rates. Water is flowing on shell side and refrigerant through tubes. The effectiveness of the heat exchanger is determined and the results achieved are presented in this paper. Significant improvements have been achieved and COP of the system is increased from 3 to 4.8.

After conducting trials on the experimental setup developed in the lab, it is found that there is significant energy saving & performance enhancement as a whole system. This is implemented as a pilot project in field on one of the bulk milk cooler of a dairy plant in Maharashtra, India which is satisfactorily working with good results and less ROI.