This is a hydraulic bench with two plexiglass tubs. The lower tub is used to heat water, while the upper one is a collection tub. Two electric heaters warm the water up to 31°C in the lower tub. Then they turn off and a circulating pump starts up and sends the water into a finned heat exchanger which is located under the bench.
The water passes through the exchanger and gives the heat to the air. Then it gets through a digital flowmeter and goes into the upper tub where there is an analogue sensor. When the water reaches the sensor, it powers up an emptying pump which is combined with an electrovalve. This valve drains the water into the lower tub.
An Arduino board measures the water temperature before and after the exchanger, it detects the flow rate from a digital flowmeter and it writes down all the system parameters, including the thermal power exchanged by a radiator in a LCD I2C display. The board also manages the pumps and the resistances (output).