Free and forced convection

wl 440


  • A vertical air duct in which the convection processes occur is the central component of the experimental unit. A fan draws in ambient air at the bottom end of the duct and guides it through the air duct.

  • Four different heating elements can be used in the air duct, which transfer their heat to the air. The heating elements have typical geometries such as tube bundle, flat plate or cylinder. The experimental unit is designed in a way that all of the heat introduced from the heating element is transferred to the air.

  • The experiments on these heating elements demonstrate how flow formation affects the heat transfer. Baffle blocks can be used to demonstrate the effects of turbulent flow on heat transfer.

Optimum incident flow to the heating elements

  • turbulence in the incident flow leads to improved heat dissipation in the more distant fluid layers

Quickly reach steady states

  • special design of the heating elements ensures rapid heating

Accurate measurement

  • controlled mixing zone behind the heating elements for accurate measurements of the mean air temperature

  • virtually all of the heat from the heating elements is transferred to the air


  • investigate heat transfer in the air duct by forced convection

  • study of free convection

  • air duct with axial fan

  • 4 heating elements with different geometries

  • continuously adjustable heating and fan power

  • display of temperatures, heating power and air velocity in the software

  • due to integrated microprocessor-based instrumentation no additional devices with error-prone wiring are required

  • functions of the GUNT software: system operation, data acquisition, educational software

  • network capability: LAN/WLAN connection of any number of external workstations with GUNT software for observation and evaluation of the experiments

  • E-Learning: online multi-media didactic materials

Learning objectives/ experiments

  • free and forced convection

  • calculation of convective heat transfer at different geometries

    • flat plate

    • cylinder

    • tube bundle

  • experimental determination of the Nusselt number

  • calculation of typical characteristic variables of heat transfer

    • Nusselt number

    • Reynolds number

  • investigation of the relationship between flow formation and heat transfer during experiments

  • description of transient heating process


  • multi-media online course, which enables learning independent of time and place

  • access via Internet browser

  • educational software including different learning modules

  • course in the fundamentals

  • detailed thematic courses

  • check through targeted review of the learning objectives

  • authoring system with editor that enables you to integrate your own, local content into the educational software


  • free and forced convection using the example of various heating elements

  • network capability: network access to ongoing experiments by any number of external workstations

  • GUNT software: operation and control of the experimental unit, data acquisition and educational software

  • E-Learning: multi-media didactic materials accessible online

Technical data

Air duct

  • flow cross-section: 120x120mm

  • height: approx. 0,6m

Heating elements, temperature limitation: 90°C

  • tube bundle

    • number of tubes: 23

    • one tube in variable postion is heated

    • heating power: 20W

    • heat transfer area: 31,41cm2

  • cylinder with an even temperature at the surface

    • heating power: 20W

    • heat transfer area: 111cm2

  • plate

    • heating power: 40W

    • heat transfer area: 2x 100cm2

  • cylinder with heating foil to investigate the local heat transfer

    • heating power: 40W

    • heat transfer area: 111cm2

Axial fan

  • max. flow rate: 500m3/h

  • max. pressure difference: approx. 950Pa

  • power consumption: 90W

Measuring ranges

  • air velocity: 0…10m/s

  • temperature: 4x 0…325°C

  • heating power: 0…50W

  • 230V, 50Hz, 1 phase

  • 230V, 60Hz, 1 phase; 120V, 60Hz, 1 phase

  • UL/CSA optional

Dimensions and weight

  • LxWxH: 670x350x880mm; Weight: approx. 25kg

Required for operation

  • PC with Windows