Usually, we do have two modes; vaporization and condensation, where each has its own profile and heat transfer coefficient for each stage. This problem is related to condensation heat transfer type. As you indicated, there are two modes; film wise and drop wise condensation. Drop wise mode is not guranteed and need special treetment, while film condensation is the usaul trend in condensation.

Dropwise condensation usually has one order of magnitude higher HTC as compared to filmwise mode at similar operating conditions, and certainly preferred in engineering heat transfer applications. However, it is not naturally occurring on surfaces of most of the heat transfer materials used in practical applications and therefore require special surface treatment. The current surface treatment to promote dropwise condensation do not last for longer times. Accordingly, filmwise mode is the most general mode of heat transfer in most of heat transfer systems and considered during the designing process. In addition, as HTC are lower in this mode of condensation, if by chance, dropwise condensation occur in the system, considering it as filmwise mode will always provides conservative estimates. Hope this clear your doubt.

Thank you Elhadi I. Dekam and Mahesh Kumar Yadav for your useful answers. Further, may we extend the technical and supportive argument for selecting film wise heat transfer coefficient in thermal equipment?

Film wise heat transfer coefficients are evaluated and taken in study. Since fouling in thermal equipment cannot be avoided and neglected. No thermal equipment is free from fouling and no fluid is clean without impurities. Film wise heat transfer coefficients are less when compared to others.

Heat transfer coefficient is evaluated generally to calculate when subjected to convection. Heat transfer coefficient is determined by empirical equations depending on flow conditions, type of flow and equipment. Scale formation in any thermal equipment is unavoidable and hence the heat transfer coefficient determined is of film wise heat transfer coefficient.

Interesting topic! Following

Thank you Hassan Izzeddin Sarsak for following.

All the heat transfer equipment suffer from fouling or scaling. This reduces heat transfer. Hence for safer side or to be in a more practical approach or to consider appropriately the heat transfer, film wise heat transfer coefficient is taken into account taking fouling into consideration.

Evaluation of heat transfer for any thermal equipment will be calculated based on drop wise or film wise heat transfer coefficient. For that, empirical relations are used to do so. However, drop wise is considered for theoretical or ideal case whereas film wise is adopted for practical or for more suitable or for most feasible. Film wise heat transfer coefficient gives an appropriate correct value based on liquid long running condition.

Using film wise heat transfer coefficient for designing thermal equipment is quite necessary, since practicality should be there. Theoretical edtimates will always be more than those from ideal.

Film wise heat transfer coefficient is used in designing of thermal equipment since, liquid is subjected to scaling because of impurities present inside. Hence, inorder to evaluate exactly,film wise heat transfer coefficient holds good.

Film wise heat transfer coefficient takes into account fouling or scaling on the equipment surfaces which lead to lower heat transfer coefficients. Due to the scale formation, it is always better and safe to consider lower values instead of no scale formation or assumed as clean surface especially for designing thermal equipment.

Film wise heat transfer coefficient is considered in evaluation of heat transfer in design of thermal equipment. In order to compensate fouling or scaling of a fluid this would be the way.

This is called film, since film is formed when the there is flow of fluid taking place in thermal equipment. As the formation of film reduces heat transfer on the walls and as the heat should pass through film and the wall before going to second fluid, film wise heat transfer coefficient got is less and is taken and considered in thermal equipment design.

Film wise heat transfer coefficient is considered in thermal equipment since theoretical evaluation is different from real practical. Due to the scale formation, there is no other way except to consider the effect of scale. Hence, filmwuse heat transfer coefficient is considered.

As a safety precaution and to have actual heat transfer coefficient in evaluating heat transfer of thermal equipment, film wise heat transfer coefficient is taken.

In designing any thermal equipment, safety is more important and for getting total heat flow, heat transfer coefficient is calculated, when calculated under convection conditions. Film wise heat transfer coefficient is considered as heat transfer coefficient, since this takes into account, fouling or scaling formed inside or outside tubes.

Film wise heat transfer coefficient is considered in any design of any thermal equipment, since this takes into account fouling or scaling aspects which reduces heat transfer and the design will come into safe limits.

There are two heat transfer coefficients which can be used, one is drop wise and other is film.wise. Film wise heat transfer coefficient gives lower values due to fouling. Hence, to be in safe condition, film wise heat transfer coefficient is considered in designing thermal equipment.

Film wise heat transfer coefficient is considered in designing of thermal equipment since this includes fouling or scaling and also as safety or taken as a practical value.

In designing thermal equipment, film wise heat transfer coefficient is considered, since any heat exchanging surface and the fluid flowing will not be clean and there will be formation of scale. Since evaluating heat transfer coefficient may lead to calculation of heat flow, for safety as well as taking into account scaling aspects, film wise heat transfer coefficient is must and to be determined.

In designing any thermal equipment, safety and precautions are to be taken. To get the heat input details, several factors are taken. One and major thing is considering film wise heat transfer coefficient which takes into account, fouling and scaling (which cannot be avoided).

I totally agree with Prof. Kishore. Film wise heat transfer coefficient has a lower value as it comprises the fouling/scaling effects. It is therefore more applicable for safety in designing the thermal equipment.

Thank you Mohamed Reda Salem and Osayed Sayed Mohamed Abu-Elyazeed for your answers.

In order to evaluate heat flow in thermal equipment, heat transfer coefficient is must. As the thermal equipment to be operated safely, film wise heat transfer coefficient is considered which takes into account fouling and scaling in it.

In designing thermal equipment, heat transfer coefficient is to be determined since the exchange of heat is mostly by convection. There are two heat transfer coefficients, one is drop wise and other film wise. Film wise heat transfer coefficient is considered, since the equipment should be on safe side, considering safety as well as taking into account fouling of fluids flowing inside and outside tubes.