HT20 – Computer Controlled Conductivity of Liquids and Gases


HT20 – Computer Controlled Conductivity of Liquids and Gases

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.


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.


Hardware Description

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.

The unit comprises a cylindrical, electrically heated, nickel-plated aluminium core surrounded by a nickel-plated aluminium sleeve. The core and the sleeve are arranged so that a uniform narrow annular gap is created between the two parts, which is filled by the liquid or gas to be analysed.

The temperature on each side of the fluid is measured by thermocouples in the surface of the core and the sleeve. HT20C adds an electronic proportioning valve and flow meter to vary and measure the flow using HT10XC. Both versions incorporate an insulated jacket to minimise heat exchange from and to the atmosphere.

The fluid to be tested is injected into the annular gap between the heated core and the cooled jacket using a hypodermic syringe. Measurement of the temperature difference between the heated and cooled surfaces together with the power supplied to the heater (measurement of DC voltage and current) using HT10XC allows the conductivity of the fluid to be calculated. The surface area and thickness of the fluid sample remain constant during all tests.

Technical Specifications

Thickness of fluid sample: 0.5mm (Fixed by the annular gap)

Nominal heat transfer area: 1.225 x10-2 m2

Gas / liquid sample volume: 6.126ml

Maximum heater power: 200W at 24V

Maximum operating temperature: 90°C (limited by integral thermostat)

Software: Supplied with HT10XC

Software capabilities: Control and logging of HT20/HT20C

Software source code: Product / HT / HT10XC

Features & Benefits


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  • Understanding the use of the Fourier rate equation in determining the rate of heat flow by conduction through liquids or gases
  • Measuring the constant of proportionality (the thermal conductivity k) of different liquids such as water and glycerol
  • Calibrating the unit for heat losses using a gas, such as air with known thermal conductivity, then measuring the temperature difference across different gases, such as carbon dioxide and helium to determine their thermal conductivity k

Note: Flammable, explosive, corrosive or toxic liquids and gases must not be used in the equipment.

HT20 ArmSoft Diagram
HT20 ArmSoft Graph of conconductivity against time for water followed by glycerine at different power inputs

  • 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


HT10XC Heat Transfer Service Unit

Optional accessories: PC to log data or control via HT10XC

  • 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 0.011m2, 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

All electrical requirements are obtained from the service unit – HT10XC

NOTE: the supply rating of the HT20/HT20C must be the same as that of the HT10XC it is used with: See ordering codes for specific requirements


Volume: 0.04m³

Gross Weight: 8Kg

Length: 0.30m

Width: 0.25m

Height: 0.16m


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