Heat-transfer equipment, condensers costs

Although the rate of heat transfer to or from fluids is improved by increase of linear velocity, such improvements are limited by the economic balance between value of equipment saving and cost of pumping. A practical rule is that pressure drop in vacuum condensers be limited to 0.5-1. Opsi (25-50 Ton) or less, depending on the required upstream process pressure. In liquid service, pressure drops of 5-10 psi are employed as a minimum, and up to 15% or so of the upstream pressure. 

The use of a jacket surrounding the reactor vessel is probably the most common method for providing heat transfer because it is relatively inexpensive in terms of equipment capital cost (see Fig. 1.10a). If heating is required, steam is condensed in the jacket or a hot heat transfer fluid stream is fed to the jacket. If cooling is required, a cooling medium is fed to the jacket. For moderate reactor temperatures (between 50 and 80°C), cooling water at 30°C is typically used. For lower temperature reactors, a cold refrigeration stream (brine) is used. 

Internal calandria, vertical short tube including vapor piping, barometric condenser, vacuum equipment, integral piping, condensate receivers. FOB cost 220000 at 45 m heat transfer area, n = 0.55 for the range 10-600. L+M = 1.6-1.9. L/M =... 

Capital costs for vapor compression systems are usually higher than for multiple-effect systems, because they are usually designed for a lower temperature difference across the evaporator. As a result, greater heat transfer surface is required. In addition, the compressor and drive are relatively expensive. Equipment costs are affected by variables such as feed properties, materials of construction, available energy supply, and calandria type. Expected maintenance and necessary spare parts must be also evaluated. Heat exchangers must be provided to exchange heat between feed and condensate and between feed and product. Other costs that must be considered, but are less easily defined, are the penalty for interrupted operation during repairs and the part load response. 

Excessive corrosion of the condensate system can lead not only to costly equipment failure and increased maintenance costs, but can also cause deposition of metal oxide corrosion products on boiler heat transfer surfaces if the condensate is recovered as feedwater. Metal oxide deposition on boiler heat transfer surfaces will result in lower fuel to steam efficiency and higher fuel costs. The deposition may also lead to tube failure due to long-term overheating. 

Minimization of construction cost has therefore been a prime objective in the development of solar distillation. Probably the most promising method for its accomplishment is the combining of all three primary elements in a distillation process—i.e., heat supply facility, evaporator, and condenser—into a single piece of very simple equipment. Such a unit is the basin-type solar distillation plant (4). But the simplicity of this equipment ceases with its general form, and over-all operation of so many functions makes the physical processes of energy and mass transfer highly complex. 

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