| The first step in preparing a heat exchanger design is assembly of the required data. The minimum requirements for basic data are as follows: Process Fluid Design Flow Rates This is normally the maximum flow rate for the process fluid at full flowsheet rates. However, there may be temporary higher rates during start up or shut down or during periods of process upset that the exchanger must perform properly with. Process Fluid Heat Duties For heating or cooling a single-phase fluid this may be expressed in terms of the temperature change. For vaporizing or condensing, one must know the quality (weight fraction vapour) and the heat duty versus the equilibrium temperature. Process Inlet Conditions The inlet temperature, pressure and allowable pressure drop for the process fluids. As will be seen later, the allowable pressure drop can have a major influence on the design of a heat exchanger. The designer should pay close attention to assigning an allowable pressure drop and ensure that it is realistic. Fouling Nature of Process Fluids This includes sufficient information so that the designer can make a decision as to how much fouling allowance to provide for in the exchanger design. Physical Properties of the Process Fluids Physical properties including at a minimum density, viscosity, specific heat and thermal conductivity are required at the inlet and outlet temperatures. In cases where there are changes of state then dew points and latent heats are also required. Materials of Construction What materials of construction are suitable for construction of the heat exchanger. |
