Air-con sensor

Engineers at Purdue University have developed a sensor-based system that indicates when air conditioners are low on refrigerant, preventing the units from working overtime.

The new system could be used in automotive air conditioners, which tend to leak refrigerant more than other types of units, and for household central air-conditioning units, according to James Braun, a professor of mechanical engineering at the university.

Maintaining the proper amount of refrigerant in a system saves energy because air conditioners low on refrigerant must operate longer to achieve the same degree of cooling as properly charged units.

‘Not only does the energy efficiency go down, but you also reduce the lifetime of the unit because it has to work harder, causing parts to wear out faster,’ Braun said.

‘It’s also very time consuming and costly to have a technician check the refrigerant and charge it up to specification.

‘To accurately learn how much charge is in the system, you have to remove all of the refrigerant and weigh it, a procedure that requires a vacuum pump and is quite time consuming.’

The new alternative method uses four sensors to monitor the temperature of refrigerant at various points along the tubing in an air-conditioning unit.

The technique is easy to use because the sensors are simply attached to the outside of the tubing, Braun explained.

A software algorithm then interprets temperature-sensor data to estimate the amount of refrigerant in the system.

Automotive air-conditioning units equipped with the new refrigerant-charge system could activate a warning light on a car’s dashboard when the air conditioner is low on refrigerant.

Alternatively, technicians servicing home air-conditioners may be able to access data from the air conditioner simply by plugging a personal digital assistant into the unit to read the refrigerant-charge information, Braun added.