Condensers design error

Common design error. Please refer back to Fig. 13.2. How can the liquid from the condenser rise to the higher elevation in the reflux drum, without being pumped Simple The pressure head of the liquid leaving the condenser is converted to elevation as the liquid flows up into the reflux drum. This works fine, as long as the liquid leaving the condenser is sufficiently subcooled. By sufficiently subcooled, I mean that when the lower-pressure liquid flows into the reflux drum, it has to be cold enough that it does not flash. 

I have often maintained that I could retire and live in luxury on the proceeds from correcting this latter common design error. The problem is easily eliminated by the addition of an intervening condensate level control drum between the reboiler and the control valve. 

In many refineries, the ratio of fresh BFW (boiler feedwater) to steam generation is so high (70-80 percent) that one has to wonder, what has happened to most of the steam condensate Mainly, due to design errors, the plant operators have been forced to divert the condensate to the sewer. 

The solution to this problem was not to repair the defective ejector condenser. This had been done before, but without preventing a repeat failure. As I ve explained in Section 25.2.2 of this text, the final or second-stage condenser serves no function. It s a design error. So in this case, as shown in Fig. 25.5, valves B and C were shut and the local atmospheric vent valve A was opened. This allowed the second-stage jet to discharge directly to the atmosphere. As a result, the pressure in the surface condenser dropped by about one-half. 

When steam pressures in the chest are near atmospheric, condensate can rise in the shell and drastically reduce avail-ahle surface—if the trap is too small to dump steam into the condensate return system or if the condensate return pressure is greater than the calculated chest pressure required. In these cases, the steam pressure will have to rise in the chest to overcome this error, if steam pressure is available. If not, the rehoiler will not deliver design flux. 

In the design of a cooler-condenser for a mixture of vapour and a permanent gas, the method of Colburn and Hougen(66) is considered. This requires a point-to-point calculation of the condensate-vapour interface conditions T( and P . A trial and error solution is required of the equation ... 

Wide span and minimal errors are two main features, A properly designed condensation hygrometer can measure dew points from 100 C down to frost poults of 75 C. 

Quite clearly, this discussion will raise many points for the designers to consider. Similarly, each of the other hazard prompts can be addressed. They will undoubtedly raise questions about the design of the venting system (toxic and flammable emissions), how to deal with a failure of the cooling water supply to the condenser, how to control and monitor the effluent discharge even under conditions of plant malfunction, instrument failure, loss of other services such as electrical supply and steam, human error, ease of safe maintenance and so on. The prompt internal fire may lead to a debate on the start-up of the system, when acetone vapour and air will be present initially. 

The magnitude of the individual coefficients will depend on the nature of the heat transfer process (conduction, convection, condensation, boiling, or radiation), on the physical properties of the fluids, on the fluid flow rates, and on the physical arrangement of the heat transfer surface. As the physical layout of the exchanger cannot be determined until the area is known, the design of an exchanger is of necessity a trial-and-error procedure. The steps in a typical design procedure are as follows ... 

Nonequilibrium, or film, methods provide physically realistic formulations of the problem that yield more accurate local coefficients at the expense of complexity. Colburn and Hougen [77] developed a trial-and-error solution procedure for condensation of a single vapor mixed with a noncondensable gas. Colburn and Drew [203] extended the method to include condensation of binary vapor mixtures (with no noncondensables). Price and Bell [204] showed how to use the Colburn and Drew [203] method in computer-assisted design. 

Severe sources of error originating from the design of the device can be heat losses through the reactor lid and badly insulated connecting tubes to and from the reflux condenser. Great care should be taken regarding these possible deficiencies. 

Remove the foil cap, discard your condensed liquid in a waste bottle designated for your unknown, and add a second 3-mL portion of your unknown liquid to the flask. Replace the foil cap, and repeat EXPERIMENTAL PROCEDURE except for the first three paragraphs until you have three error-free runs. New squares of aluminum foil are available if you need them, but remember that you must reweigh the dry flask and foil if a new piece is used. 

Loss of volatile vapor out vent, high vent gas temperature, degree of subcooling < design and unusual temperature profile between vapor inlet and condensate outlet instrument error/underdesign. 

Process phenomena which are possible would be operator errors induced spiUs or overflows. Evaporator or condenser leaks could also occur. Since the ded iterization and HAM i ems are not designed to withstand a DBE, the probability of dther em rrieasing radionuclides is equal to the probability of the occurrence of a DBE, which equals 2.0x1 (Ref. 8-33). 

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