Armfield - Heat Transfer - HT10XC Computer Controlled Heat Transfer Teaching Equipment

The Armfield Linear Heat Conduction accessory has been designed to demonstrate the application of the Fourier Rate equation to simple steady-state conduction in one dimension.

The units can be configured as a simple plane wall of uniform material and constant cross sectional area or composite plane walls with different materials or changes in cross sectional area to allow the principles of heat flow by linear conduction to be investigated. Measurement of the heat flow and temperature gradient allows the thermal conductivity of the material to be calculated. The design allows the conductivity of thin samples of insulating material to be determined.

On the HT11C the heater power and the cooling water flow rate are controlled via the HT10XC, either from the front panel or from the computer software. On the HT11 these are controlled manually.

Key Features

• A small-scale accessory to introduce students to the principles of linear heat conduction, and to enable the conductivity of various solid conductors and insulators to be measured
• Comprises a heating section, a cooling section, plus four intermediate section conductor samples and two insulator samples
• The heating section, cooling section and one of the intermediate sections are fitted with thermocouples (eight in total) evenly spread along the length of the assembled conduction path
• All sections are thermally insulated to minimise errors due to heat loss
• Includes a water pressure regulator and a manual flow control valve
• Computer-controlled unit includes an electronic proportioning solenoid valve to control the cooling water flow rate and a water flow meter
• Heater power variable up to 60W
• Water flow rate variable up to 1.5 l/min
• Heating and cooling sections, 25mm diameter
• A comprehensive instruction manual is included

The Armfield Radial Heat Conduction accessories have been designed to demonstrate the application of the Fourier rate equation to simple steady-state conduction radially through the wall of a tube.

The arrangement, using a solid metal disk with temperature measurements at different radii and heat flow radially outward from the centre to the periphery, enables the temperature distribution and flow of heat by radial conduction to be investigated. On the HT12C the heater power and the cooling water flow rate are controlled via the HT10XC, either from the front panel or from the computer software. On the HT12 these are controlled manually.

Key Features

• A small-scale accessory to introduce students to the principles of radial heat conduction, and to allow the conductivity of a solid brass disk to be measured
• Comprises a brass disk with a heater at the centre and a cooling water tube attached to the periphery
• Six thermocouples measure the temperature gradient between the heated centre and the cooled periphery of the disk
• Thermally insulated to minimise errors due to heat loss
• Includes a water pressure regulator and a manually operated valve to control the flow rate
• Computer-controlled unit includes an electronic proportioning solenoid valve to control the cooling water flow rate, a pressure regulator and a water flow meter
• Heater power variable up to 100W
• Water flow rate variable up to 1.5 l/min
• Conduction disk is 110mm diameter and 3.2mm thick

This Armfield accessory has been designed to demonstrate the laws of radiant heat transfer and radiant heat exchange using light radiation to complement the heat demonstrations where the use of thermal radiation would be impractical. The equipment supplied comprises an arrangement of energy sources, measuring instruments, aperture plates, filter plates and target plates, which are mounted on a linear track, in different combinations, to suit the particular laboratory teaching exercise chosen.

Key Features

• ​A small-scale accessory designed to introduce students to the basic laws of radiant heat transfer and radiant heat exchange
• A heat source with radiometer and a light source with light meter are used where appropriate to demonstrate the principles
• The heat source consists of a flat circular plate 100mm in diameter which incorporates a 216W electric heating element (operating at at 24V DC maximum)
• The light source consists of a 40W light bulb (operating at 24V DC maximum) mounted inside a housing with a glass diffuser
• The heat and light sources, instruments, filters and plates are mounted on an aluminium track with graduated scale, which is designed to stand on the benchtop and connect to the Heat Transfer Service Unit without the need for tools
• A comprehensive instruction manual describing how to carry out the laboratory teaching exercises in radiant heat transfer/exchange and their analysis as well as assembly, installation and commissioning is included

A hot surface loses heat (heat is transferred) to its surroundings by the combined modes of convection and radiation. In practice these modes are difficult to isolate, so an analysis of the combined effects at varying surface temperature and air velocity over the surface provides a meaningful teaching exercise.

The heated surface studied is a horizontal cylinder, which can be operated in free convection or forced convection when located in the stream of moving air. Measurement of the surface temperature of the uniformly heated cylinder and the electrical power supplied to it enables the combined effects of radiation and convection to be compared with theoretical values. The dominance of convection at lower surface temperatures and the dominance of radiation at higher surface temperatures can be demonstrated as can the increase in heat transfer due to forced convection.

On the HT14C, the heater power and the air flow are controlled via the HT10XC, either from the front panel, or from the computer software. On HT14 these are controlled manually.

Key Features

• ​​A small-scale accessory to introduce students to the principles of combined convection (free and forced) with radiation from a horizontal heated cylinder
• Comprises a heated cylinder mounted in a vertical air duct, with a fan at the base of the duct, which can be used to provide a variable air flow over the cylinder
• Heater rating 100W at 24V DC
• K-type thermocouples measure the air temperature upstream and the surface temperature of the cylinder
• On the computer-controlled unit, the air flow is electronically adjustable over the range 0-7 m/s by a variable-speed fan, otherwise it is manually adjustable
• The air flow rate is measured by a vane-type anemometer in the outlet duct
• The accessory is mounted on a PVC baseplate, which is designed to stand on the bench top and connect to the Heat Transfer Service Unit without the need for tools
• A comprehensive instruction manual is included

A long horizontal rod, which is heated at one end, provides an extended surface (pin) for heat transfer measurements. Thermocouples at regular intervals along the rod allow the surface temperature profile to be measured. By making the diameter of the rod small in relation to its length, thermal conduction along the rod can be assumed to be one-dimensional and heat loss from the tip can be ignored. The measurements obtained can be compared with a theoretical analysis of thermal conduction along the bar combined with heat loss (heat transferred) to the surroundings by the modes of free convection and radiation simultaneously.

Key Features

• A small-scale accessory designed to demonstrate the temperature profiles and heat transfer characteristics for an extended surface when heat flows along the rod by conduction and heat is lost along the rod by combined convection and radiation to the surroundings
• The extended surface comprises a 10mm-diameter long solid brass rod mounted horizontally and heated at one end with a 20W, 24V DC heater
• Eight thermocouples mounted at 50mm intervals along the rod provide the temperature distribution
• The temperature of the ambient air is measured by an independent thermocouple
• 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
• A comprehensive instruction manual is included

Radiative heat transfer between a thermometer and its surroundings may significantly affect the temperature reading obtained from the thermometer, especially when the temperature of a gas is to be measured while the thermometer ‘sees’ surrounding surfaces at a higher or lower temperature than the gas. The error in the reading from the thermometer is also affected by other factors such as the gas velocity over the thermometer, the physical size of the thermometer and the emissivity of the thermometer body.

In this equipment a group of thermocouples are used to measure the temperature of a stream of air, at ambient temperature, passing through the centre of a duct while the wall of the duct is elevated in temperature to subject the thermocouples to a source of thermal radiation. Each thermocouple gains heat by radiation from the heated wall and loses heat by convection to the air stream and conduction along the wire. The net result is an increase in the temperature of the thermocouple above the temperature of the air stream which it is supposed to measure. The result is an error in the reading from the thermocouple. A radiation shield can be positioned in the duct to show the effect of screening the thermocouples from thermal radiation from the duct wall.

On the HT16C the heater power, the air flow rate and the position of the radiation shield can all be controlled via the HT10XC, either from the front panel controls or from the software. On HT16, these parameters are adjusted manually.

Key Features

• A small-scale accessory to demonstrate how temperature measurements can be influenced by sources of thermal radiation
• Comprises three K-type thermocouples with different styles of bead mounted in a vertical air duct. A fan at the base of the duct provides a variable air flow over the cylinder. A band heater heats the duct wall adjacent to the thermocouple beads
• Heater rating 216W at 24V DC
• K-type thermocouples measure the air temperature upstream and the surface temperature of the heated duct section
• On the computer-controlled unit the air flow is electronically adjustable over the range of 0-9 m/s by a variable-speed fan, otherwise it is manually adjustable
• The air flow rate is measured by a vane-type anemometer in the outlet duct
• A radiation shield can be lowered over the thermocouples to demonstrate the improvement in reading accuracy when the thermocouples are shielded from the source of radiation
• 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
• A comprehensive instruction manual is included

Analytical solutions are available 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. Each shape is allowed to stabilise at room temperature then suddenly immersed in a bath of hot water at a steady temperature. Monitoring of the temperature at the centre of the shape allows analysis of heat flow using the appropriate transient-temperature/heat flow charts provided.

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.

Key Features

• A small-scale accessory 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
• Analytical transient-temperature/heat-flow charts are supplied for each of the shapes
• The water bath heater is 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
• A comprehensive instruction manual is included

Based on a Peltier device, the Armfield HT18C Thermo-electric Heat Pump demonstrates how electrical power can be used to extract heat from a cool surface and transfer it to a hot surface.

This effect is becoming widely used for point cooling (eg of semiconductor devices) and small-scale volumetric cooling. The HT18C is designed for use with the Armfield HT10XC Heat Transfer Teaching Equipment.

Key Features

• Small-scale accessory designed to demonstrate the use of a Peltier device to transfer heat across surfaces
• Comprises a Peltier device, a heater, and a water-cooled heat exchanger
• Heat transfer rates up to 68W
• Heater power, Peltier drive and cooling flow rate all fully electronically adjustable under computer control
• Measurement of cooling water temperatures and flow to allow an overall energy balance
• The accessory is mounted on a PVC baseplate, which is designed to stand on a benchtop and connect to the heat transfer service unit without the need for tools
• A comprehensive instruction manual is provided
• Software is provided

The Armfield Free and Forced Convection unit has been specifically designed to demonstrate the phenomena of natural (free) and forced convection. Temperature profiles and heat flux over three different heat transfer surfaces can be easily studied.

The HT19 is designed for use with the Armfield HT10XC Heat Transfer Teaching Equipment.

Key Features

• A bench mounted unit specifically designed to demonstrate the phenomena of free and forced convection and to measure temperature profiles from three different heat transfer surfaces
• Comprises a vertical air duct, with a transparent front for visibility mounted on a fan at the base of the duct, three heat transfer surfaces, air flow, and temperature probes
• Technical data is included for each of the three heat transfer surfaces, which will enable students and researchers to compare practical results with theoretical analysis for free and forced convection
• Three heat transfer surfaces supplied: a flat plate surface area 0.011 m2, pinned extended surface area 0.0525m2, and finned extended surface area 0.1414m2
• Vertical duct incorporates a transparent front wall allowing complete visualisation of the process and identification of the air flow and temperature sensors
• Each heat transfer surface is fitted with its own heater (240W) and thermocouples, to enable easy interchange
• All heat transfer surfaces incorporate guards to permit safe use outside of the duct for performing free convection experiments
• ArmSoft software includes separate exercises for each of the heat transfer surfaces in free or forced convection and records of all measured variables for analysis and comparison of the performances
• K-type thermocouples measure the air temperature in the duct before and after the heater, as well as the surface temperature of the heat transfer surfaces
• The air flow is manually adjustable up to 10 m/s
• The air flow is measured by an air-velocity sensor, which is inserted inside the duct
• Mounted on a PVC baseplate which is designed to stand on the bench top and connect to the Heat Transfer Service Unit with simple plug-in connections
• A comprehensive instruction manual is included

The Armfield Conductivity of Liquids and Gases unit has been specifically designed to enable students to measure and compare the thermal conductivities of various liquids and gases. It’s designed to facilitate quick and effective cleaning and to minimise thermal losses.

The HT20 / HT20C is backwards compatible with the HT10XC, so if you already own an HT10XC, you can easily expand the teaching potential with the addition of this accessory.

Key Features

• Thickness of the fluid sample is restricted to 0.5mm to minimise convection in the fluid sample
• Concentricity of the heated and cooled surfaces is accurately maintained using a spiral insulator
• Trapped bubbles of the previous liquid or gas sample are prevented by the spiral flow path when injecting a different liquid or gas
• ArmSoft software is supplied, with separate exercises for determining the thermal conductivity of liquids and gases