DESCRIPTION

Technical Description

Under real conditions, the heat transport between two objects is normally substance-bound, i.e. convection and/or heat conduction, and not substance-bound, i.e. radiation, at the same time. Determining the individual heat quantities of one type of transfer is difficult.
The WL 377 trainer enables users to match the individual heat quantities to the corresponding type of transfer. The core element is a metal cylinder in a pressure vessel. A temperature-controlled heating element is located at the centre of the cylinder. Sensors capture the wall temperature of the cylinder and the heating power. This metal cylinder is used to examine the heat transfer between the heating element and the vessel wall.
The pressure vessel can be put under vacuum or positive gauge pressure. In the vacuum, heat is transported primarily by radiation. If the vessel is filled with gas and is under positive gauge pressure, heat is also transferred by convection. It is possible to compare the heat transfer in different gases. In addition to air, nitrogen, helium, carbon dioxide or other gases are also suitable.
A rotary vane pump generates negative pressures down to approx. 0,02mbar. Positive gauge pressures up to approx. 1bar can be realised with compressed air. Two pressure sensors with suitable measuring ranges are available for the pressure measurement: the negative pressure is captured with a Pirani sensor; a piezo-resistive sensor is used for experiments with a filled cylinder.
The measured values can be read on digital displays. At the same time, the measured values can also be transmitted directly to a PC via USB, where they can be analysed with the GUNT software.

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

Learning Objectives / Experiments

Experiments in vacuum
- heat transfer by radiation
- determination of the radiation coefficient
  
Experiments at ambient pressure or positive gauge pressure
- heat transfer by convection and radiation  
- determination of the heat quantity transferred by convection 
- determination of the heat transfer coefficient based on measured values
- theoretical determination of the heat transfer coefficient based on the Nusselt number
- comparison of the heat transfer in different gases