GTW Series Heat Flux Transducers

Product Details

Medtherm GTW Series Total Heat Flux Transducers offer dependable direct measurement of heat transfer rates in a variety of applications due to careful design, rugged quality construction and versatile mounting configurations. Each transducer will provide a self-generated 10-millivolt (nominal) output at the design heat flux level. Continuous readings from zero to 150% design heat flux are made with infinite resolution. The linear transducer output is directly proportional to the net heat transfer rate absorbed by the sensor.

Medtherm GTW Series transducers have been used on thousands of application challenges, including ground and flight aerospace testing, fire testing, furnace development, flammability standards, heat transfer research, materials development and more.

GTW Series transducers are a water cooled total heat flux transducer which provides a linear EMF output directly proportional to the net absorbed heat transfer rate to the sensing tip. The standard output is 10 to 20 millivolts at the design full scale heat flux level. The transducer is designed for use in the cone calorimeter flammability test apparatus. Each unit is supplied with an individual calibration traceable to the National Institute of Standard and Technology (NIST).

Features
Specifications

Medtherm GTW Series

Schmidt-Boelter gages absorb the heat at one surface and transfer the heat in a direction normal to the absorbing surface. The EMF output is generated by a multi-junction thermopile responding to the difference in temperature between the surface and a plane beneath the surface. The Schmidt-Boelter thermopile sensor is always used below 5 Btu/(ft²⋅s). It can be optionally specified up to 100 Btu/(ft²⋅s).

GTW Series Heat Flux Transducer

Heat flux is absorbed at the sensor surface and is transferred to an integral heat sink that remains at a different temperature than the sensor surface. The difference in temperature between two selected points along the path of the heat flow from the sensor to the sink is a function of the heat being transferred, and a function of the net absorbed heat flux. At two such points, our transducers have thermocouples/thermopiles to form a differential thermoelectric circuit, thus providing a self-generated EMF at the output leads that is directly proportional to the heat transfer rate.

Features

Linear Output
Output Proportional To Heat Transfer Rate
Accurate, Rugged, Reliable
Convenient Mounting
Uncooled, Water Cooled, Gas Purged Models
Radiometer And Limited View Accessories
Measure Total Heat Flux
Measure Radiant Heat Flux

Construction

Accuracy, Ruggedness and reliable sensors.
Long Transducer Life And Signal Stability are enhanced by the massive body of OFHC copper.
Protection against rough handling in mounting is provided by a stainless steel flange when specified.
Signal Integrity is protected by the use of welded connections, stranded lead wire with braided copper shielding and Teflon insulation firmly secured in the transducer body with strain relief to ensure resistance to rough handling and stray signals.

Accessories

Removable Window Attachments, with the standard sapphire or optional window materials, are available to limit the basic transducer to measurement of radiation heat flux only.
View Restrictor Attachments are available to limit the angle of view for the basic transducer to 60°, 30°, 15°, or 7° for narrow view angle measurements.
Direct Reading Heat Flux Indicators Models H-201, H-203, and H-204 are available for direct digital readout in any heat flux units from any linear heat flux transducer input. An amplified analog output is provided on some. Ask for Bulletin.
Body Temperature Thermocouple measurement can be provided by an optional copper/constantan 24 AWG solid conductor thermocouple, with TIG welded junction and Teflon insulated duplex wire.

Standard Ranges Available: Full scale design heat flux level: 4000, 3000, 2500, 2000, 1500, 1000, 500, 250, 200, 100, 50, 30, 25, 20, 15, 10, 5, 2, 1, 0.5, 0.2 Btu/(ft²⋅s). (Custom ranges available.)
Output Signal: linear output, 10 millivolts nominal at full range.
Maximum Allowable Operating Body Temperature: 400 °F.
Overrange Capability: to 150% range for 2-1000 Btu/(ft²⋅s) ranges.
Maximum Non-Linearity: ±2% of full range.
Repeatability: ±1/2%
Calibration Expanded Uncertainty: ±3% for ranges to 250 Btu/(ft²⋅s), coverage factor k=2, for approximate 95% confidence level.
Sensor Absorptance (Hemispherical): Gardon gages, .92, nominal, from 0.6 to 15.0 µm. Thermopiles, .95, nominal, from 0.6 to 15.0 µm.
Spectrum Transmitted By Sapphire Window (When used): 85%nominal from 0.15 to 5.0 µm. Other window materials are optional.
Lead Wire: 24 AWG stranded copper twisted pair, Teflon insulation over each, braided copper shield, Teflon jacket overall, 36″ standard length with stripped ends. (The optional body thermocouple wire is 24 AWG Teflon/Teflon insulated duplex solid conductor.)
Time Constant: (63.2% response to a step radiant heat Input)
- 250 to 4000 Btu/(ft²⋅s): less than 50 ms
- 50 to 200 Btu/(ft²⋅s): less than 100 ms
- 2 to 30 Btu/(ft²⋅s): less than 250 ms
Sensor Type: (Standard, options available)
- 5 to 4000 Btu/(ft²⋅s): Gardon Gage (Except S-B for 64P-5 models)
- 0.2 to 4 Btu/(ft²⋅s): Schmidt-Boelter (Schmidt-Boelter sensors are also available as an option from 5 to 100 Btu/(ft²⋅s) ranges.
Nominal Impedance: (with standard leadwire)
- Less than 10 ohms on Gardon Gages
- Less than 250 ohms on Schmidt-Boelter Gages.
Heat Capacity of Uncooled Units: Energy that can be absorbed by transducer in an adiabatic installation (defined as all surfaces perfectly thermally insulated except for 1-inch diameter sensor face) before exceeding the 400 °F maximum body temperature limitation: Model without water cooling provisions: 6.2 Btu, Models with water cooling provisions but without water: 4.2 Btu
Maximum Purge Gas Pressure: 150 psi over ambient