Abstract:

An automatic detection and control system of in-situ testing equipment studying rock and soil thermophysical properties applied  ground-source heat pump theory is inroduced. This testing equipment pumps constant heat current into the ground heat exchanger by detecting and controlling the temperature difference of the exchanger entry and exit. This system is composed of the upper and the lower computer systems. In the upper computer system, an industrial computer is used as the core of detection and control, a configuration software is installed in it. The operation interfaces of the whole system and the software system are programmed by the configuration software. The lower computer system is composed of two analog-digital conversion intelligent modules and a programmable logic controller (PLC). Two intelligent modules are applied to collect various parameters, and the PLC is applied to export the control signal, then control the actuator. Based on 4 experiments in different geothermal wells of 72 hours for each one, this automatic detection and control system achieved accurate control of temperature difference of the exchanger entry and exit continuously. The control precision is lower than 0.1℃.

Key words: configuration software, intelligent module, PLC, rock and soil thermophysical properties, temperature control, PID control