Optimization Analysis For Heat Exchange Network In The Building Heat Environment Control

Building energy saving is the focus of the modern society’s development, andbuilding air conditioning system’s energy saving is the key point of buildingenergy-saving. In the building heat environment control system’s heat exchange web,heat pump system, supply system and heat transfer conductances’ integratedoptimization is the core problem. And the influences analysis of periodical heattransfer is also the key problem. Based on that, this thesis studies the built heatenvironment control system from a fresh view of heat transport process and makesthe research:Firstly, the optimization principle of sensible heat transfer web: in the single heatsource and single cool source heat transfer web, minimum equivalent thermalresistance is equal to the optimal heat transfer efficiency;. And the optimal thermalcapacity ratio expression of three fluids for the series heat exchangers is got and thebest distribuition of heat transfer conductance is averaged, when the equivalentthermal resistances of sub-exchangers are the same. For the typical refrigeration circleprocess, the minimum entransy addeness and entropy generation are consisitant withmaximum energy efficiency; when the thermal capacity flow of two fluids are thesame, the best design is averaged heat transfer conductance distribution.Secondly, the mathched characterist is important for heat transfer web. For thecounter-flow heat exchanger, unmatched coefficient represents the ratio of equivalentthermal resistance to thermal resistance (1/KA). When the thermal capacity flow oftwo fuild is the same, the two flows are matched and the non-matched coefficient isminimum, equal to1. Adopting temperature difference to analyze the single stageheat pipe exchanger, the constant temperature characterist of refrigerant makes thethermal capacity low un-matched, which results in the low efficiency of heat transfer.Modifing the single stage to multiple stages heat pipe reduces the un-matchedcoefficient and improves the heat transfer effieincy.Thirdly, pomot the integrated optimization method for supply system and heatpump system: first getting the optimal thermal capcatiy flow ratio and heat conductance ratio, and then getting the optimal thermal capcatiy flow. For the heatpump system, the main influence of the optimal thermal capcatiy flow is the piperesistance coefficient ratio of two fluids. When the pipe resistance coefficient ratio is1, the optimal thermal capcatiy flow ratio is1and heat conductance ratio is1. Bringup the optimal pump power curve’s expression to gain the optimal thermal capacityflow and price ratio or marginal benefit method to integrate the heat exchangerconductance and supply system’s power.Then, give out energy storage heat exchanger model to analyze the periodic heattransfer process, which can be regarded as equivalent heat source and cold source’snon-simultaneous heat transfer process, and the medium plays the role of heat storageand indirect heat transfer. Point out the expressions of heat transfer quantity for theflat in different heat transfer bounderies. Heat resistance method is proposed toanalyze the periodic process.Finally, analyze the application effect of the research contribution, based onexamples of integrated air-conditioning’s flow ratio and heat conductance distribution,temperatue difference and temperature of cooled water in the temperature andhumidity independent control air conditioning system, and several typical period heattransfer process.