View
232
Download
7
Category
Tags:
Preview:
DESCRIPTION
hjkhjkhkjkjj huhkuhk jhnknjkk jkknjknjk
Citation preview
PRESENTATION NAME
Condensation Heat Transfer boiling, condensation : high heat transfer rates understand the processes to design the appropriate heat-transfer equipmentModes of condensationDropwise/filmwise condensationDirect/Indirect/homogeneous condensationModes of condensationIn vertical flat plate, Tw < Tsat : condensate will form at surface.Dropwise condensation: liquid does not wet the surface, droplets are formed.Filmwise condensation: liquid wets the surface, smooth film is formed. The surface is blanked by the film, which grows in thickness as it moves down the plate.Filmwise Condensation
Dropwise Condensation
Homogeneous Condensation
Direct Contact Condensation
CondensationIn the remaining lecture we now focus on indirect contact filmwise condensation
General approach to condensation
General approach to condensation
Condensation on Flat Plate
Nusselt Analysis - Assumptions
Mass flow of condensateHeat transfer at wall Amount of condensate added between x and x+dxThus
Heat transfer coefficient
In term of Nusselt number
For vertical plates and cylinders and fluids with Pr > 0.5 and cT/hfg 1.0
For non-linear temperature profile
For laminar film condensation on horizontal tubes
To determine flow (laminar or turbulence) use Renolds number
Critical Re is 1800For Vertical plate of unit depth, P = 1 For Vertical tube, P = d
Relate mass flow with total heat transfer and heat transfer coefficient
Using 20 % safety factor in design problems
For inclined surfacesCondensation number (Co)
For condensation of refrigerants at low vapor velocities inside horizontal tubesFor higher flow rates
Recommended