SELECTION CRITERIA BETWEEN HORIZONTAL  CONDENSER AND VERTICAL CONDENSER 

• Selection of the orientation of the condenser plays important role in the design. If someone selects wrong orientation then condenser will not give the desired performance.

Some selection criteria between horizontal condenser and vertical condenser are described as below:

1.  Only for the case of     filmwise condensation, horizontal position givers higher     condensation coefficient than vertical position. In filmwise condensation, the thickness of     condensate film on the heat transfer surface governs the value of the condensation coefficient. With horizontal position and shell side condensation, the condensate travels less distance over the heat transfer surface before detaching from the heat transfer surface and falling down by gravity compared to the vertical position. With vertical position, condensate travels over the entire tube length before falling down by the effect of gravity. 

Hence average condensate film thickness in the case of horizontal position is less than that of obtained in the case of vertical position and hence, it can provide higher condensation coefficient.

2.  In case of condensation with     subcooling in a shell & tube heat exchanger, condensation coefficient is higher for horizontal position but the subcooling coefficient is higher for vertical position.

In case of subcooling with horizontal position, small fraction of gravitational force is acting on the pool of condensate and hence, condensate is flowing with almost no turbulence (Laminar flow). Hence, subcooling with horizontal position is natural convection heat transfer. While in subcooling with vertical position, entire gravitational force is acting on pool of condensate. Hence, it creates turbulence in pool of condensate and provides higher subcooling coefficient (Turbulent flow). Subcooling with vertical position can be considered as forced convection heat transfer. 

 

Therefore, in case of condensation with subcooling, shell and tube heat exchanger is design for both position (Vertical and Horizontal) and the position which gives higher value of the overall heat transfer coefficient is selected.

3.  In case of condensation with non-condensable, selection of position depends on the percentage of non-condensable present in inlet vapour. For which guidelines are given by Frank.

(a) If non-condensable are < 0.5% (by mass), then the presence of noncondensables is ignored in design calculations. Heat exchanger is designed as a     total condenser. For this case, horizontal position should be selected as it provides the higher condensation coefficient.

 

(b) If non-condensable are > 70% (by mass), then for the entire flow rate, without phase change correlation is applied to calculate the heat transfer coefficient. However, in calculation of heat duty (ft), condensation is considered. For this case, selection of the position does not depend on heat transfer coefficient, as without phase change coefficient does not depend on position of heat exchanger so in this case position is decided by other factors like available area or available height.

 

(c) Between 0.5 to 70% non-condensable, heat transfer coefficient is determined by considering both condensation as well as cooling of non-condensable and vapours. For this case horizontal position should be selected as it gives higher condensation coefficient, if condensation with cooling is carried out on shell side. If the same is carried out on tube side, then vertical position is better, because dry gas film over the heat transfer surface is continuously swept away by incoming stream.