Equipment sizing heat exchangers

Equipment Sizing Heat Exchanger Design Tower Design... 

If the optimum size heat exchanger for the initial plant is installed, an additional exchanger either in parallel or in series will be required when the plant is expanded. This may be the best option when the heat transfer involves condensation and subcooling. The exchanger can be designed to perform both functions initially, and then when the plant is expanded an aftercooler can be installed and the initial equipment can act only as a condenser. 

The internals of the bubble column reactor may have a dramatic impact on the flow patterns of the bubbles and the liquid. Companies have not divulged details about the internals to date. Some details of the US DOE pilot plant (22.5 inch 0.57 m diameter) have been published [ 106]. In this report the dimensions of the cooling tubes, their location, and their number are provided. These cooling coils occupied about 10% of the total volume of their commercial reactors slurry volume. The gas holdup and bubble characteristics as well as their radial profiles were determined in a column that was about the size of the US DOE reactor [107-109]. Dense internals were found to increase the overall gas holdup and to alter the radial gas profile at various superficial gas velocities. The tube bundle in the column increased the liquid recirculation and eliminated the rise of bubbles in the wall region of the column. These results indicate that further studies of bubble column hydrodynamics are directed toward larger scale units equipped with heat exchange tubes. 

Now we go to sizing the equipment. We start with the heat exchanger. Sizing Heat exchangers We select the first one, equipment number 1 in the flowsheet. The... 

Perform an energy balance. Estimate cooling water, refrigeration, and fuel requirements. Size heat exchange equipment if needed for an assessed plant inventory. 

If exchangers are countercurrent devices, then the number of units equals the number of shells, providing indithdual shells do not exceed some practical upper size limit. If, however, equipment is used that is not completely countercurrent, as with the 1-2 shell and tube heat exchanger, then... 

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. 

Published Cost Correla.tions. Purchased cost of an equipment item, ie, fob at seller s site or other base point, is correlated as a function of one or more equipment—size parameters. A size parameter is some elementary measure of the size or capacity, such as the heat-transfer area for a heat exchanger (see HeaT-EXCHANGETECHNOLOGy). Historically the cost—size correlations were graphical log—log plots, but the use of arbitrary equation forms for correlation has become quite common. If cost—size equations are used in computer databases, some limit logic must be included so that the equation is not used outside of the appHcable size range. 

Also important is the interplay between different sensors, controllers, automation equipment, and objects regulated by the control equipment. The requirements of pumps, fans, batteries, heat exchanger, valves, motors, etc. in standard sizes may greatly differ from the theoretical calculations. Because of this fact, the control equipment, in addition to satisfactory control, must be capable of correcting the differences between the calculated and delivered subproducts. 

Conservation is a general concept widely used in chemical engineering systems analysis. Normally it relates to accounting for flows of heat, mass or momentum (mainly fluid flow) through control volumes within vessels and pipes. This leads to the formation of conservation equations, which, when coupled with the appropriate rate process (for heat, mass or momentum flux respectively), enables equipment (such as heat exchangers, absorbers and pipes etc.) to be sized and its performance in operation predicted. In analysing crystallization and other particulate systems, however, a further conservation equation is... 

Circulatory systems often use an intermediate header tank, from which the bearings are supplied by gravity. The complete system may comprise, in addition and according to the size of the installation, heat exchangers or coolers, filters, strainers, settling tanks, centrifuges and other purifying equipment. 

Calculations predict that improved heat transfer for reacting systems in micro-channel heat-exchanger reactors could lead to considerable size reduction of the equipment, by enhancing the degree of product formation per micro channel (see Figrue 1.24) [140, 141]. This was exemplarily shown for a fast, high-temperature... 

Example 2.1 A new heat exchanger is to be installed as part of a large project. Preliminary sizing of the heat exchanger has estimated its heat transfer area to be 500 m2. Its material of construction is low-grade stainless steel, and its pressure rating is 5 bar. Estimate the contribution of the heat exchanger to the total cost of the project (CE Index of Equipment = 441.9). 

Figure 3.1b illustrates how the investment in the heat exchanger is optimized. As the amount of recovered heat increases, the cost of energy for the system decreases. On the other hand, the size and capital cost of the heat exchange equipment increase. The increase in size of heat... 

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