Abstract:

In this research would be planned to optimize the utilization of boiler exhaust gas by adding a heat exchanger to the chimney to heat the incoming water to the boiler. The types of heat exchangers are very diverse and each is designed to meet specific needs, but the shell and tube type is by far the most widely used type due to its relatively simple construction and reliability because it can be operated with several types of working fluids. Optimization of the design of this heat exchanger was done by full factorial method using four independent variables, namely diameter, length, distance between pipes and pipe angles with three levels of experimentation so that 81 calculated data were obtained. The result of full factorial optimization obtained the highest value of design displacement coefficient (Ud) of 354 W/m2oK.This condition is obtained at the outer diameter of the pipe 0.0127m, the arrangement of pipes 45o, the distance between the pipes is 1.25 and the length of the pipe 1.2 m. This heat exchanger has a maximum heat transfer capacity of 64.8 kW with a water mass flow rate of 0.1761 kg/second, an average temperature difference of LMTD 109.3 oK and has an effectiveness of 26.41 %. Thermal validation of manual and CFD calculation results did not show a significant difference. Manual calculation of water output temperature is in the range of 80.5 oC and the result of CFD 76 oC and exhaust gas calculation is 110 oC and CFD 114 oC.

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