1. Design indicatorsThe design indexes of heat exchanger include working fluid type and its flow rate, inlet and outlet temperature, working pressure and heat exchanger efficiency.Heat exchangers for aerospace equipment should also include the allowable pressure drop, size and mass.1. Design indicatorsThe design indexes of heat exchanger include working fluid type and its flow rate, inlet and outlet temperature, working pressure and heat exchanger efficiency.Heat exchangers for aerospace equipment should also include the allowable pressure drop, size and mass.
2. General layout.The general arrangement of the heat exchanger should first select the type and structure of the heat exchanger, the form of fluid flow and the materials used, and then select the type of heat transfer surface.Consider operating temperature, pressure, etc.
3. Thermal design.The thermal design of heat exchanger includes heat transfer calculation, flow resistance calculation and determination of size.Thermal design in addition to the technical performance indicators, also need to have on the surface of the heat transfer characteristics (including heat transfer characteristics and flow resistance characteristics and structural parameters) and thermal physical property parameters of fluid and material, can speak optimization techniques used in the design of the heat exchanger, according to the design goal, for the selected forms of heat exchanger and heat transfer surface, through the different Angle optimization analysis, offer several alternatives.
4.Structural design.The mechanism design of heat exchanger includes the following contents:
(1) determine the material and size of each part according to the working temperature and working pressure, as well as the results of thermal design and resistance calculation, so as to ensure the performance of the heat exchanger in stable operation.
(2) select welding method and sealing material according to working temperature, pressure and fluid property.
(3) with the goal of ensuring the uniformity of fluid distribution, design the head, header, connection and baffle.
(4) in order to meet the thermal and resistance performance of the structural design, the main parts must be strength check, in order to avoid in the limit working state due to insufficient strength, resulting in damage or selection of too thick and resulting in waste.
(5) maintenance (including cleaning, repair and maintenance, etc.) and transportation requirements should be considered.For some heat exchangers working under special conditions, some must calculate their thermal stress during start-up and shutdown, calculate the structural vibration caused by fluid flow, or check the flow rate in order to reduce corrosion and structure.In short, structural design and thermal design have the same importance, the design of heat exchangers need to take into account at the same time, and should be coordinated with each other.
5. Design scheme selection.After the thermal design and structure design of the heat exchanger is completed, the alternative scheme of the structure is provided, and then the designer makes the evaluation according to the criterion.Make a choice by considering specific conditions.The choice of conditions is qualitative, such as mold manufacturing conditions, brazing furnace size, transportation restrictions, delivery date, company policy and competitive intensity will affect the choice.Evaluation criteria refer to the indicators that can be quantified and measured, such as weight, external dimensions, pumping fluid consumption, initial investment and life span.
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