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WL 440 Free and forced convection



  • Free and forced convection using the example of various heating elements1
  • Functions of the GUNT software: educational software, data acquisition, system operation1
  • Part of the GUNT-Thermoline: Fundamentals of  Heat Transfer


Technical Description

Convection is one of the three basic forms of heat transfer. Material-bound heat transport takes place. During convection the fluid is in motion.

The WL 440 offers basic experiments for targeted teaching on the topic of free and forced convection on various heating elements.

At the heart of the experimental unit is a vertical air duct into which various heating elements are inserted. An axial fan is located on top of the air duct. The fan draws in ambient air and guides it through the air duct. The air flows past a heating element and absorbs heat. Four heating elements with different geometries are available to be selected. In order to investigate free convection, two of the four heating elements can be operated outside of the air duct. The experiments on all heating elements demonstrate how  flow formation affects the heat transfer. The heating elements release heat only at their surface. The compact design ensures rapid heating.

The experimental unit is equipped with temperature sensors at the inlet and outlet of the air duct. The air velocity is measured to determine the air flow rate. Heating power and air flow rate are adjusted and displayed via the software.

The microprocessor-based instrumentation is well protected in the housing. The GUNT software consists of a software for system operation and for data acquisition and an educational software. With explanatory texts and illustrations the educational software significantly aids the understanding of the theoretical principles. The unit is connected to the PC via USB.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

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


[1] investigate heat transfer in the air duct by forced convection
[2] study of free convection
[3] air duct with axial fan
[4] 4 heating elements with different geometries
[5] continuously adjustable heating power and fan power
[6] display of temperatures, heating power and air velocity in the software
[7] microprocessor-based instrumentation 
[8] functions of the GUNT software: educational software, data acquisition, system operation
[9] GUNT software via USB under Windows Vista or Windows 7

Technical Data

Heating elements
- tube bundle: heating power 20W
- cylinder: heating power 20W
- plate: heating power 40W
- cylinder for circumferential measurement: heating power 40W
Axial fan
- max. flow rate: 500m³/h
- nominal speed: 9500min-1
- power consumption: 90W

Measuring ranges
- air velocity: 0...10m/s 
- temperature: 4x 0...325°C
- heating power: 0...50W

Dimensions and Weight
LxWxH: 670x350x880mm
Weight: approx. 25kg Required for Operation 230V, 50Hz, 1 phase

Scope of Delivery
1 experimental unit
4 heating elements
1 CD with authoring system for GUNT educational software 
1 CD with GUNT software + USB cable
1 set of instructional material

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