Heat Exchanger

Introduction A Heat exchanger is a device that transfers thermal energy from a high temperature fluid to a low-temperature fluid with both fluids moving through the device. Examples in practice in which flowing fluids exchange heat are air intercoolers and pre-heaters, condensers and boilers in steam plant, condensers and evaporators in refrigerator units, and many other industrial processes in which a liquid or gas is required to be either cooled or heated. In HEAT EXCHANGER, there are usually no external heat and work interactions.

TYPES OF HEAT EXCHANGER:- Heat exchangers can be classified according to construction specification or direction of flow of the two fluids, discussed as follows-

1. Construction feature- 3. MODES

Recently, in their second and third papers (Naphon and Wongwises [14,15], mathematical models to determine the performance and heat transfer characteristics of spirally coiled finned tube heat exchangers under wet-surface conditions and dry-surface conditions were developed Analysis of Heat Transfer by Cascading Spiral Inner Tube in a Heat Exchanger 10 and investigated. There was reasonable agreement between the results obtained from the experiment and those from the developed model. As mentioned above, only a few works on the heat transfer characteristics in spiral coil heat exchangers have been reported.

The literature survey revealed that though many researchers have investigated the use of different geometries on plate surface to enhance heat transfer, there is still a dearth of work to explain what type of geometry provides best heat transfer enhancement for a specific thermal boundary condition. And also some of the literatures were unable to make any conclusions about friction factor for such type of problems. The project work conducted focused on study of variation in heat transfer and friction factor in flow through cascaded spiral inner tube heat exchanger. The results obtained from

and the outlet temperature of hot and cold water , friction factor will also be taken into consideration. Fabrication and experimental investigation of system CFD analysis of heat exchanger. To validate effect of heat transfer enhancement. To determine and fiction factor through flow simulation.

Methodology:-

1. Experimental Analysis 2. Numerical Investigation

Flow assumptions:-

Following are the assumptions which are been made in the computation of the problem. (a) The flow turbulent. (b) The flow non-reacting. (d) The flow is incompressible (i.e. ⍴=constant)

Design Assumption: No phase change occurs; both fluids are single phase and are unmixed. Heat losses to surrounding are negligible. The temperature in the fluid streams is uniform. The fluids have constant specific heats. The fouling resistance is negligible.

Heat transfer analysis procedure:-

Step 1- Calculate discharge at various voltage and find fluid velocity

Discharge=volume/Time=V/t

Velocity=Dicharge/(cross section area)=Q/A

Step 2- calculate Reynolds number and mass flow rate

Re=⍴UiDh/µ

Step 3 – convective heat transfer coefficient

h=0.023k/d