Heat exchanger rating program

For fan failure on air coolers, credit may be taken for normal convection according to API 521. The credit shall be 25% of the normal design duty. In case precise calculation is required, a check shall be performed for natural convection using a heat exchanger rating program. In case of a water-cooled cooler, credit is not allowed if the cooling water flow stops. 

Software such as HTRl computer programs are available to calculate heat tiamferarca required for a specified duty and flow conditions (design calculation) oi to calculate flow outlet conditions for an existing heat exchanger (rating calculation). 

For many pieces of equipment, such as heat exchangers and distillation columns, stand-alone programs are available that calculate material and energy balances around that piece of equipment, size the equipment, and calculate or rate its performance. 

The results from the rating program are either the outlet temperatures of streams, if the length of the heat exchanger has been fixed, or the length of the heat exchanger required... 

The flow rate of the dissolution medium through the cell must be specified for each product. The USP recommends a flow rate between 4 and 16ml/min with an allowance of 5%. Manual operation and sampling for this type of test can be tedious and the system can be automated to control the pump, heat exchanger and test procedure, and deliver samples to a fraction collector. The system can be programmed to switch between different media at predetermined time points to allow pH changes during the test. 

The flow of water required to cool the oil is 23310 Ib/hr. The computer program PROG83 rates the double pipe heat exchanger using either fin tubes or bare tubes. Table 8-23 lists the input data and output of the computer program. The fin efficiency is 43.3 percent and the computed overall heat transfer coefficient is 27.3 Btu/hrft °F. The pressure drops have not been exceeded, and the double pipe exchanger will be satisfactory for the service. 

THIS PROGRAM RATES DOUBLE PIPE HEAT EXCHANGERS USING BARE TUBES OR LONGITUDINAL FINNED TUBES. 

FIGURE 6.54 Rating program core block of the heat-exchanger design process. 

A schematic diagram of the apparatus for TPA measurements is shown in Figure 8.40. The polymer samples, 1 x 0.125 0.014 in., were heated in a copper tube furnace thai was programmed for a temperature rise of 50cC/h. Hydrogen was passed over the sample at a 3 mL sec flow rate, but because the condensation nuclei counter required a gas flow of lOOmL/s, additional amounts of nitrogen were added beyond the furnace and heat exchangers. Some materials studied by this technique are shown in Table 8.7. 

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