• Demonstration of the relationship between input power and surface temperature in free convection.
  • Demonstration of the relationship between input power and surface temperature in forced convection.
  • Demonstration of the use of extended surfaces to improve heat transfer from the surface.
  • To determine the temperature distribution along an extended surface.


  • Frame made of stainless steel
  • Process flow diagram in front of panel
  • Investigate heat transfer in the air duct by forced convection.
  • Study of free convection.
  • Air duct with Centrifugal fan.
  • 3 heating elements with different geometries.
  • Continuously adjustable heating power.
  • Continuously adjustable fan power to vary air velocities in the duct.
  • Anemometer to measure air velocity entering in the duct.
  • Measurement of air temperature at inlet and outlet of duct.
  • Measurement of surface temperature for heat exchangers.
  • Display of temperatures, heating power and air velocity.
  • Safety devices and control for protection of system
  • Spares will be supplied for smooth operation for the period of 1 year.
  • The unit will be provided with all required accessories for smooth running, gases with cylinders (where required), calibration kits (if required), installation & after-sale services, maintenance services and operational manuals.

Heat transfer by Free & forced Convection in a vertical duct is carried out in this unit. Convection is one of the three basic types of heat transfer. In this process the whole fluid moved from warm zones into cold zones. The vertical duct is constructed in such a way that the air temperature and velocity can be readaily measured. A fan provides the air stream in a duct for forced convection experiments. A control panel contains temperature measurement, power control and fan speed control circuits with appropriate instruments. Air velocity measured with anemometer mounted on the duct.

Heat transfer by simultaneous conduction and convection, whether free or forced, forms the basis of most industrial heat exchanger and related equipment. The measurement and prediction of heat transfer coefficients for such circumstances is achieved in the Free & Forced Convection Heat Exchanger by studying the temperature profiles and heat flux in an air duct with associated flat and extended transfer surfaces. The vertical duct is so constructed that the air temperature and velocity can be readily measured, and a variety of plug-in modules of heated solid surfaces of known dimensions can be presented to the air stream for detailed study.

A Control Panel contains temperature measurement, power control, and fan speed control circuits with appropriate instrumentation. Temperature measurement, to a resolution of 0.1oC is effected using thermocouple sensors with direct digital read-out in oC. Air velocity is measured with anemometer mounted on the duct. The power control circuit provides a continuously variable, electrical output of 0~100 watts with a direct read-out in watts.

Using the instrumentation provided, free and forced convective heat transfer coefficients may be determined for:-

  1. A flat surface
  2. An extended finned surface
  3. A extended pipe surface

Each module may be used independently on the bench, to establish free convection coefficients for horizontal orientation.

The apparatus is fully self-contained.

Technical Data

Air duct

  • Flow cross-section: 120x120mm
  • Height: 1000mm

 Heating elements

  • Temperature limitation: 90oC

 Flat surface

  • Heating power: 150W
  • Surface area: 0.013m2

 Extended Pipe bundle

  • Number of tubes: 20
  • Heating power: 150W
  • Heat transfer area: 0.051m2

 Extended Finned Bundle

  • Number of  fins: 7
  • Heating power: 150W
  • Heat transfer area: 0.14m2

Centrifugal fan

  • Max. flow rate: 500m3/h
  • Max. air velocity: 10m/s
  • Power consumption: 90W

 Measuring range

  • Air velocity: 0~10m/s
  • Temperature: 4x -100~400oC
  • Heating power: 0~100W

 Scope of Delivery

  • 1 experiment unit
  • 1 pipe bundle surface
  • 1 fined surface
  • 1 flat surface
  • 1 instruction manual