A Simple Device for Monitoring Flow Rates in Thermosyphon Solar Water Heaters

Direct measurements of fluid flow rates in thermosyphon solar water heaters in the field are difficult. This paper reports on an activity to develop, calibrate, and evaluate a simple device for such measurements. A suitable device should have the following general characteristics: low pressure drop, rugged, inexpensive, simple, nondisruptive, low power requirements, and reasonably accurate. Moderate success has been achieved in satisfying all of these requirements with a hydrogen bubble generator (utilizing the electrolysis of water) in a clear plexiglass tube mounted in a vertical section of the flow line in which the flow is upward. The rate at which the hydrogen bubbles are swept along with the water can be used (when calibrated) to indicate the flow rate.