CHF01, CHF02

Change-of-heat-flux sensors

CHF01 and CHF02 are sensors for studying small thermal effects that usually remain hidden. This is attained by the direct measurement of changes in heat flux. The application of the CHF sensors typically is in the detection of chemical reactions and phase changes in industrial processes. Typical applications are in quality control of composite processing and in chemical process monitoring.

Figure 1 the working principle of CHF sensors. In case of a thermal process that follows a temperature trajectory according to line (2), a small temperature change (1), for instance due to a chemical reaction or a phase change, is hardly visible in the temperature signal. The CHF signal “amplifies” such minor events and facilitates the detection and analysis.

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INTRODUCTION

In many chemical processes it is interesting to detect the occurrence of reaction steps. A typical process is equipped with temperature and pressure sensors; in general the information of these is sufficient. CHF sensors are designed to look in more detail; by detecting changes in heat flux one can detect otherwise invisibly small thermal effects.

CHF DESIGN

CHF sensors essentially employ two differential temperature sensors. These sensors are stacked, and electrically connected in anti-series, creating a single output.

Model CHF01 has been designed for low temperatures up to 260 degrees C, while CHF02 is specifically meant for higher temperature / high flux applications.

CHF installation should be done with care; in particular the CHF tip should be in good thermal contact with the phenomenon to be measured. Thermal pastes may be used to promote contact. Holes for mounting are typically drilled with a 0.2 mm higher diameter than the probe diameter.

 

 

Figure 2 CHF sensor working principle. Differential temperature sensors (1) and (2) stacked and electrically in anti-series, CHF tip (3), CHF tube with temperature sensor(4), spring loaded bolt (5), wiring out with change-of-heat-flux and temperature wiring (6), metal vessel or mould (7), reacting substance (8).

SUGGESTED USE

Quality assurance of critical chemical reactions

Quality assurance of composite processing

Monitoring of chemical processes

General quality control of production

MORE INFORMATION / OPTIONS

Alternative designs: Hukseflux is specialised in CHF design. Alternative models, for instance more robust or temperature resistant have been manufactured on request.

Depending on the application, amplifiers AC100 or NAM01 are used.

CHF SPECIFICATIONS

• Temperature sensor: Thermocouple K, ANSI MC96. 1-1982
• Protection sensor tube: IP 68
• Protection metal sheathed cable IP 68
• Protection Teflon cable: IP 67

CHF01

• Temperature range (total sensor including cable): -55 to +260 °C

• ordering code: CHF01/L1/L2, L1, L2 in mm

• standard: CHF01/30/2500

• response time (1/e): 1 s (typical in steel)

• probe diameter: 4 mm

CHF02

• Temperature range (total sensor including metal sheathed cable): -55 to +450 °C

• Temperature range (Teflon cable): -55 to +260 °C

• ordering code: CHF02 /L1/L2/L3, L1, L2, L3 in mm

• standard: CHF02/30/100/2500

• response time (1/e): 4 s (typical in steel)

• probe diameter: 2 mm
• options: extended to 700 °C (no spring)

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