Unsteady State Heat Transfer Apparatus (MODEL ME-HT-915E-R)
The ARL’s HT-915E Apparatus is used for temperature distribution and heat flow as a function of time and position for simple solid shapes which are suddenly subjected to convection with a fluid at a constant temperature. Simple shapes are provided together with appropriate classical transient-temperature/heat flow charts which allow a fast analysis of the response from actual transient measurements.
An independent thermocouple mounted alongside the shape indicates the temperature of the water adjacent to the shape and provides an accurate datum for measurement of the time since immersion in the hot water.
- A Standard Apparatus designed to enable exercises to be performed in unsteady-state heat transfer
- Comprises an electrically heated water bath, variable-speed recirculation pump, a set of solid thermal shapes and a shape holder
- The shapes supplied comprise a rectangular slab, a long cylinder and a sphere. Two of each shape are supplied, manufactured from brass and stainless steel, respectively. Each shape is instrumented with a thermocouple to monitor the temperature at the centre of the shape
- The water bath heater is 1.5kW/3KW. The water bath includes an integral flow duct and a thermocouple to measure the water temperature
- The circulating pump ensures hot water flows past the solid shape under evaluation at constant velocity during the test. It is a variable-speed DC pump
- The accessory is mounted on a PVC baseplate, which is designed to stand on the benchtop and connect to the Heat Transfer Service Unit without the need for tools
The HT-915E equipment consists of a heated water bath together with set of instrumented shaped test pieces. Each of the shapes incorporates a thermocouple to measure the temperature at the centre of the shape.
A total of six shaped test pieces are provided, ie three simple shapes (a rectangular slab, a long solid cylinder and a solid sphere) each manufactured in two different materials (brass and stainless steel). Measurements taken on a shape in one material can be used to confirm the conductivity of a similar shape constructed from a different material. Transient-temperature/heat-flow charts are supplied for each of the shapes.
A circulating pump mounted alongside the water bath draws water from the bath and returns it at the base of a vertical cylindrical duct, which is located inside the water bath at the centre.
A holder ensures each of the shapes is quickly and correctly positioned within the vertical duct for measurements to be taken.
The upward flow of water at constant velocity past the shape ensures the heat transfer characteristic remains constant and also ensures the water surrounding the shape remains at a constant temperature. The rate of water recirculation can be varied by using the HT10XC to adjust the DC voltage on the pump.
The shape holder has been carefully designed to eliminate the need to touch the shape while its temperature stabilises in air, and also to position the shape accurately inside the water bath while transient measurements are taken.
A thermocouple mounted on the shape holder contacts the hot water at the same instant as the solid shape and provides an accurate datum for temperature/time measurements.
A thermostat allows the water to be heated to a predetermined temperature before taking measurements. The large volume of water in the bath ensures that any change in the temperature of the water, as the measurements are taken, is minimal.
The water bath is heated by a mains powered electrical heater, and protected by a residual current device for operator safety. A thermocouple located in the water bath enable the temperature of the water to be monitored and adjusted to the required temperature.
Bodies of different size, shape and material are allowed to stabilise at room temperature then dropped into the hot water bath.
The change in temperature of each body is monitored. Analytical temperature/heat-flow charts are used to analyse the results obtained from different solid shapes. The results obtained from one shape can be used to determine the conductivity of a similar shape constructed from a different material.