Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up. Download Free PDF. Gerard Hawkins. A short summary of this paper. Download Download PDF. Translate PDF. GBH Enterprises, Ltd. Process Engineering Guide: GBHE-PEG-HEA Selection and Design of Condensers Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the information for its own particular purpose.
GBHE gives no warranty as to the fitness of this information for any particular purpose and any implied warranty or condition statutory or otherwise is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed. It describes the various factors which influence the choice of exchanger, giving some of the options and detailing their merits and draw-backs.
The Guide also gives advice on design methods for condensers. It does not attempt to give detailed design procedures, most of which are in any case performed by computer programs, but points the reader to sources of information. It does give advice on many of the additional design features which are not covered by the programs. A co-operative research organization, in the UK, involved in research into the fundamentals of heat transfer and two phase flow and the production of design guides and computer programs for the design of industrial heat exchange equipment.
A co-operative research organization, based in the USA, involved in research into heat transfer in industrial sized equipment, and the production of design guides and computer programs for the design of such equipment. An organization of US manufacturers of shell and tube exchangers. In the case of multi-component systems, which condense over a temperature range, the key temperature is the final temperature to which the product is to be cooled.
For temperatures above ambient the choice is usually between air and cooling tower water. See Clause 5. The cold service fluid used in the process exchangers may be either a single phase liquid or a boiling liquid. With boiling liquid coolants, the working fluid of the refrigeration plant is generally used directly as the coolant, the process exchanger becoming the evaporator of the refrigeration cycle, and the vapor being returned to the suction of the compressor.
On some plants, e. This will reduce the load on the refrigeration system, which is an expensive form of cooling. A combination of air cooling followed by water cooling is sometimes used for wide temperature ranges above ambient. In recent years there has been an increased tendency to heat integration on plants. If a suitable process stream is available, it can be used as the coolant.
However, it should be remembered that the control requirements of the plant may impose a fluctuating demand on the coolant, which may influence the operability of the total exchanger network. A special case of heat integration in distillation columns is mechanical vapor re-compression, where the overhead vapor is compressed and condensed at a higher temperature to provide the heat input to the column reboiler.
In the former case, the condenser has to be mounted above the top plate of a trayed column or the distributor of a packed column. The use of a gravity reflux return may also impose a lower design pressure drop for the condenser than is necessary for a pumped system.
With a pumped reflux system, the designer has more flexibility. However, the potential savings in mounting the condenser near grade level must be offset against need for a pump and the increased cost of vapor and liquid pipework to link the condenser with the top of the column. Moreover, a pumped reflux system usually requires a reflux drum; for a gravity return system, particularly if the top product is to be removed as vapor, it may be possible to dispense with this. The latter favors either an internal condenser or a reflux condenser dephlegmator , where the condensate flows counter-current to the vapors.
Air cooled exchangers require a relatively large plot area. Because of this, it may be difficult to find a suitable location for one which would allow gravity condensate return. There are many ways in which this can be done. The choice of method depends amongst other factors on whether the vapor is totally condensed, or the top product leaves as a vapor. Some of the methods can be applied to any type of condenser, but others are specific to certain designs.
With a single phase coolant the obvious way to do this is to throttle back the supply of coolant. However, if the coolant side is prone to fouling which is velocity dependent, this can cause problems. Cooling water is particularly bad in this respect; low velocities may lead to both high fouling and corrosion of metals.
This requires control of the refrigerant feed rate to match the varying plant demands. Partly because of this, most process refrigerant cooled exchangers are designed as shell and tube exchangers with shell side boiling, usually as kettle boilers, as this allows easy control of the liquid level and disengagement of the vapor. Control of heat load can be effected by varying the pressure, and hence evaporation temperature, of the refrigerant.
For a single component, there is no vapor film resistance, but for multi- component systems, including single condensables with inerts, it can be substantial.
The value of the condensate film resistance depends on the geometry of the condensing surface, and on whether the process is dominated by gravity or vapor shear. In the absence of vapor shear, on vertical surfaces the condensate film resistance initially rises with increased condensate loading, and then falls again. On the outside of horizontal tubes, or inside horizontal passages, the resistance generally rises with increased loading. Vapor shear effects reduce the resistance, unless the vapor is flowing counter-current to the condensate, when they may increase it.
The full analysis for other than binary systems is extremely complex; even for binary mixtures the calculations are tedious. It can be seen from the above that high condensing side coefficients are favored by high vapor velocities, both to improve the condensate film coefficient and to give a good gas phase coefficient. Unfortunately, pressure drop also rises with vapor velocity, limiting the velocity that can be used. During the course of condensation, the vapor flow falls, causing a reduction in coefficients.
This can be particularly important in the latter stages of a condensation with small quantities of non-condensables present, where very poor coefficients can result. These effects can be reduced in some designs of condenser by reducing the flow area as the condensation proceeds.
For example, the number of channels per pass in a multi-pass exchanger can be reduced for the later passes. For a shell and tube exchanger with condensing on the shell side, the baffle pitch can be decreased at the cold end of the exchanger. Where it is not practical to reduce the flow area, it may be worth considering dividing the duty into two, with a small vent condenser following the main unit.
In practice, the exit condensate is generally at a lower temperature than the vapor, and the vapor may be super- or sub-saturated with respect to one or more components.
This can be particularly important when the vent from a condenser is exiting to the environment. Unfortunately, suitable reliable programs for calculating these cases are not available and hand calculations are difficult. If this is important, a heat transfer specialist should be consulted. Moreover, for a given flowrate the pressure drop rises as the pressure falls.
This can be particularly critical for vacuum condensers. As the high velocities which tend to give high pressure drops also result in good heat transfer, some compromise may be necessary, but particular attention should be given to minimizing the parasitic pressure losses which occur in regions away from the heat transfer surface, such as the nozzle pressure drops.
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Next SlideShares. You are reading a preview. Create your free account to continue reading. Sign Up. Upcoming SlideShare. Selection and Design of Condensers. Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Share Email. Top clipped slide. JayPrince s, Thanks for the support, keep on visiting for more upcoming posts, Regards, Pharma Engineering.
Whats the solvent you are trying to evaporate, and tell me weather the reaction mass is an pure compound or not?? Regards, Pharma Engineering. Mr Ajay pls I need your email address cos I have a lot to learn from you Kingsleyewansiha74 gmail.
Dear sir, you have mentioned that latent heat does not depend upon the temperature. But if you look at the steam tables we can clearly see that latent heat changes with the temperature and also of course with pressure. Dear , Latent heat is a function of pressure.
Temperature is also a function of pressure. Once refer clausius clapeyron equation. Pharma Engineering. Thursday, 21 April design. Ajay Kumar Kalva Calculations , Condenser , design.
I am Ajay Kumar Kalva , Currently serving as the CEO of this site, a tech geek by passion, and a chemical process engineer by profession, i'm interested in writing articles regarding technology, hacking and pharma technology. Read more. Labels: Calculations , Condenser , design.
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