A waste heat recovery system heat by plate heat exchangers and performance evaluation in textile industry

Textile industry is one of the heading sectors in Turkey and plays an important role in country?s economy. Including dye process there is a great amount of heat waste in many textile processes. These waste liquids and gases have crucial energy saving potential. Dyeing plants are considerably loose heat energy. During the process it could be possible to save energy by employing a waste heat recovery system for the plants. Waste liquids having lower temperatures emit to the environment, while providing energy saving. The aim of this study is to apply waste heat recovery system by employing a plate heat exchanger that provides heat transfer from hot waste liquids to the clean cold water at a selected dyeing plant. The effectiveness of the heat exchanger and exergy (the second law) efficiency were considered to be one of the performance parameters. Objectives of this study are to achieve thermodynamical and economical analyses of the waste heat recovery system for the textile industry. The waste heat recovery system including a plate heat exchanger installed to a dyeing plant which dyes cotton and synthetic fibers, located in Usak Industrial Park. The system was modeled thermodynamically. Inlet and outlet temperatures data of waste heat source and clean cold water for different mass flow rates has been obtained. The optimum operation condition was determined by integrating the first and the second law of thermodynamics for a counter flow plate heat exchanger employed for a dyeing process. The economical analysis was presented by net present value method and the payback time of he investment was calculated. Furthermore, improvements on production process and increased production efficiency have been evaluated. As a consequences, optimum cold water and waste water mass flow rates were found to be between 7,00 m³/h and 10,00 m³/h respectively. While the waste water inlet temperatures varies between 52,4°C and 59,5°C, exergy destruction rate, exergy efficiency, and effectiveness of the plate heat exchanger have the values from 5,40 to 9,46 kW; from 68, % to 61,6 %, and from 0,969 to 0,924 respectively at the optimum mass flow rates. The payback time of the system was calculated by net value method was 10 months.It was recorded that the amount of the natural gas required to the dyeing process was reduced in the amount of 28,36% for 1 kg of cotton fibers by employing the waste heat recovery system. Due to the decrease in the processing time, the efficiency of the process is increased.