چكيده به لاتين
Abstract:
Compact heat exchangers with more than 700 m2/m3 heat transfer area per unit volume and less than 6 mm hydraulic diameter have been very useful in engineering especially in HVAC. Nowadays, due to increasing scarcity of energy resources, design and optimization of all types of heat exchangers are gaining more impotence. Compact heat exchangers are a category of heat exchangers. In this category of heat exchangers, both hot and cold sides increase heat transfer area by fins. Some of the commonly used fins are: “wavy”, “offset strip”, “louver”, “perforated”, and “plain fins”. In this thesis we focus on “offset strip fins” with high compactness, high heat transfer efficiency and high reliability that are widely employed in heat exchangers for cooling systems of aircrafts, automobiles, and HVACs. In addition, offset strip fins have higher strength and reliability than louver fins.
This thesis presents a case study (based on a restaurant in Yerevan, Armenia) on thermal modeling, cost modeling, and optimal design of compact plate-fin heat exchanger with rectangular offset strip fins which themselves can act as energy recovery or heat recovery units within air handling unit. The ε-NTU method has been applied to thermal modeling (the heat exchanger’s effectiveness and pressure drop estimation). Fin height, fin thickness, fin pitch and fin offset length were considered as four design parameters. Multi objective optimization using genetic algorithm was applied to obtain the maximum effectiveness and the minimum total annual cost (sum of annual investment and operation costs) as two objective functions. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto Optimal Solutions’. LINMAP decision-making method was applied to select the best optimal solution. The result of this study revealed 0.88 effectiveness and 504.90 ($/year) total annual cost for plate-fin heat exchanger with rectangular offset strip fins. The payback was 25024.88 ($/year) within the period of 10 months. The sensitivity analysis of change in optimum effectiveness and total annual cost with a change in design parameters (electrical energy price and supply air temperature) of the plate-fin heat exchanger was also performed and the results has been reported.
Keywords: Energy Recovery Ventilation or Heat Recovery Ventilation (ERV or HRV), Plate-Fin Heat Exchanger, Rectangular Offset Strip Fins, Multi-Objective Optimization, Genetic Algorithm (GA).
