tailieunhanh - Design and Optimization of Thermal Systems Episode 2 Part 7

Tham khảo tài liệu 'design and optimization of thermal systems episode 2 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 372 Design and Optimization of Thermal Systems be a natural one such as a lake or a constructed cooling pond the condensers of the power plant and the water pumping system consisting of pumps and piping network as considered in Example . The requirements for a successful design involve both the recirculation which raises the temperature at the intake and the thermal effects on the body of water. Thus the heat transfer and flow in the water body have to be modeled and coupled with the condensers and the pumping system. Design variables include the locations and dimensions of the inlet outlet channels as well as the dimensions and geometry of the pond itself. Operating conditions such as discharge temperature and flow rate must also be considered. Various flow configurations may be considered to curb the effects of recirculation see Figure . For instance the outlet may be moved as far away as possible from the inlet or a wall may be placed as an impediment between the two. Computer simulations of the cooling pond including the heat transfer to the surroundings and the flow due to intake and discharge and of the pumping system are used to provide the necessary inputs for design and optimization. Since recirculation effects are reduced but pumping costs increased as the separation between the intake and discharge is increased a minimization of the cost for acceptable temperature rise at the intake may be chosen as the objective function. Clearly the design of the system is a major undertaking and involves many subsystems that Hot water inflow Outflow FIGURE The flow system for power plant heat rejection to a body of water a Top view b front view. Acceptable Design of a Thermal System 373 make up the overall system. Over the years the power industry has developed strategies to design and optimize such systems. The design process is fundamentally the same for large and small systems and the basic approach presented in this and earlier chapters can easily be