Double pipe heat exchanger• Two sets of concentric pipes, two connecting tees, and a return head and a return bend.• A device whose purpose is the transfer of thermal energy between two fluids.• Heat Exchanger-HX• Common applications: Boilers, Coolers, Condensers, Evaporators.• Common design consists of tow fluids separated by a conducting medium.
Classification Heat transfer mechanism Degree of surface compactness Heat transfer type Flow arrangement Number of passes Construction
Classification Direct contact type: Cooling towers, Spray towers Indirect contact type Cooling tower Spray tower
Classification Single Pass arrangement Multiple pass arrangement
Classification The choice of a particular flow arrangement depends upon the required heat exchanger effectiveness, fluid flow paths, allowable thermal stresses, temperature levels and other design criteria. Heat exchangers may be classified according to their flow arrangement. • Parallel-flow • Counter-flow • Cross-flow • Divided-flow • Split-flow
Classification The heat exchangers classify based on geometry of construction are, • Plate Heat Exchangers • Extended surface Heat Exchangers • Tubular Heat Exchangers
Classification Plate Heat Exchanger • Limited to below 25 bar and 2500C • Plate heat exchangers have three main types : gasketed ,spiral and lamella heat exchangers. • The most common of the plate-type heat exchangers is the gasketed plate heat exchanger
Classification Plate Heat Exchanger Aadvantages • Plate heat exchangers yield heat transfer rates three to five times greater than other types of heat exchangers. • The design of the plate heat exchanger allows to add or remove plates to optimize performance, or to allow for cleaning, service, or maintenance. • Plate exchangers offer the highest efficiency mechanism for heat transfer available in industry.
Classification Plate Heat Exchanger Disadvantages • Plate exchangers are limited when high pressures, high temperatures, or aggressive fluids are present. • Because of this problem these type of heat exchangers have only been used in small, low pressure applications such as on oil coolers for engines.
Classification Extended surface heat exchangers • Plate fin heat exchanger • Tube fin heat exchanger Tube fin exchanger Plate fin exchanger
Classification Tubular heat exchanger• Material and design development• Widely used• No limit to range of temperatures and pressures• Two types 1. Double pipe heat exchanger 2. Shell and tube heat exchanger
Classification Double pipe heat exchangerThey consist of one pipe concentrically located inside asecond larger pipe. Double pipe exchanger
Classification Phase change heat exchangers• Condensers(water cooled, air cooled)• Reboilers• Evaporators Induced draftForced draft Air cooled condenser
Classification Phase change heat exchangers Water cooled condenser
Classification Area density: Ratio of heat transfer area to the volume of heat exchanger Compact Heat exchanger • Area density greater than 700 m2/m3 or 213 ft2/ft3 or hydraulic diameter ≤ ¼ inch for gas stream. • Area density greater than 400 m2/m3 or 122 ft2/ft3 for liquid stream). Non-compact Heat exchanger • Area density less than 700 m2/m3 for gas stream. • Area density less than 400 m2/m3 for liquid stream.