Portable electronic divided bar

(Australian Patent Application 2007903695)

Hot Dry Rocks Pty Ltd introduces what we believe to be the world’s first portable, electronic divided bar machine for measuring the thermal conductivity of solid samples. This device has grown out of HDRPL’s extensive experience measuring thermal conductivity of rock samples, in collaboration with a team with over a decade of experience building specialist geophysical tools. The design has focused on functionality, portability and versatility, without compromising on simplicity, accuracy and reliability.

Description:

A divided bar is a device that applies a steady thermal gradient across a sample in series with a material of known thermal conductivity. The thermal conductivity of the sample is calculated by measuring the ratio of the thermal gradient across the sample relative to that across the known material. A “conventional” divided bar maintains the thermal gradient using thermostatically controlled water baths. These baths are bulky and require AC power and (usually) a source of running water to cool the pump motors. Such devices are only found in permanent laboratories. In contrast, our device operates from a 12 volt DC power source (with optional AC adapter) and requires no external cooling. Thethermal gradient is created using electronic Peltier devices, which have the ability to both heat and cool in response to an applied electric current.

Features and specifications:

• 12 volt DC power supply, with AC converter
• Temperature at hot and cold plates kept constant to within ±0.02°C
• Temperature differential adjustable to 10°C, 15°C or 20°C
• Calibrated between 1.5–9.0 W/mK
• Achievable accuracy ±2%
• Replaceable temperature measurement pads calibrated by HDRPL
• Simple controls
• Dimensions: approx 26 cm wide, 28 cm deep, 28 cm high
• Weight: approx 8 kg
• Robust construction

Advantages over a conventional divided bar:

• No water source required: The device is cooled by a built-in PC fan unit.
• Rapid response time: The low thermal bulk of the Peltier devices mean that operating temperature is reached rapidly and can be varied quickly.
• Field portable: Light, maneuverable and robust construction with field portability in mind.
• Variable measurement temperature: Mid-point temperature variable in 5°C increments over a range of ±10°C from ambient temperature.
• Quiet: Only the noise of the cooling fan.
• Compact: Incorporates all major components of a conventional divided bar set-up in one unit.

Applications:

• Standard equipment for a thermal properties laboratory
• Make thermal conductivity measurements at core storage sites
• Measure thermal conductivity of fresh core samples during remote drilling operations
• Investigate the temperature dependence of thermal conductivity over a range of 20°C

Enquiries:

HDRPL will custom-build units upon request with a delivery time of 8–12 weeks. Please address all enquires to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .