What is the Rovac Air-Conditioning System in Automotive?

The Rovac Air-Conditioning System is used in automotive vehicles. This system implies the air as the refrigerant. This is a combination of rotary compressor/expander units. In this article, I will discuss the details and the features of the Rovac Air-Conditioning system.


Rovac Air-Conditioning System

This system of air-conditioning of the car uses air. It is yet to be commercially deployed in cars. Dr. Thomas C. Edwards has designed the system. It is a rotary vane air cycle air-conditioning system. The refrigerant, or air, did not go through a phase transition from liquid to gas and back again, which was a flaw in the ROVAC design.

Heat can be absorbed (transferred) very effectively and efficiently when there is a change in condition. Heat can also be transferred by compressing and depressurizing air, however not very successfully. Rovac seemed very clever at first glance in that it used air as the refrigerant + a large rotary vane compressor, but the air is inefficient as a refrigerant in that it requires far more energy to evoke the required refrigerating effect than a conventional automobile air conditioner – in short, it wasn’t viable.

Read More- Gas Turbine Cycles | Open Cycle and Closed Cycle Gas Turbine.

Features of Rovac Air-Conditioning System

The system has the following distinguishing features:

  1. lt docs do not use Freon gas. Hence, there is no high-pressure gas to store, seal against leaks, or replace. The system is thus much simpler.
  2. It has a highly co-efficient performance when compared with the conventional type. This makes the system consume less power of the engine and hence there is fuel economy.
  3. It gives instant Cold. There is no detectable time lag from start-up to cold air.
  4. It gives instant This makes the heat available from intermediate coils for defrosting long before the engine gets warmed up.

Read More- What is the Importance of Maintenance of Automobiles?

Function of Rovac Air-Conditioning System

ROVAC system alternately compresses and expands the air. The conventional sealed units use a reversed Rankine cycle with a gas-to-liquid and back-to-gas phase change. ROVAC uses no phase change like the conventional sealed units, except for the incidental moisture normally present in the air. Edwards calls this a reversed Brayton cycle.

The oval-shaped housing acts as a compressor on the inlet side and an expander on the exhaust side. The air enters the compressor at atmospheric pressure and passenger compartment temperature. This air is compressed to a pressure of about 21 N/cm and a temperature of about 140°C. From the compressor, the travels through the heat exchanger which is provided with fins.

The heat exchanger has large tubes. The inside air is cooled by the outside air flowing past the tubes. This drops the temperature of the inside air to 45°C. There is no appreciable change in the pressure.

Now, this air is lead through the expander where the pressure drops to atmospheric and the temperature of the air drops to about 6°C. This air is circulated inside the passenger compartment, thus cooling the occupants. The cycle gets repeated.

It may be mentioned that the ROVAC can be designed to produce outlet temperatures well below the freezing point. Modulation and moisture control are handled in the distribution ducts. It is worth mentioning that when the hot air passes through the expander, it returns part of its heat energy to the vaned rotor, thus saving engine power.

Read More- Environmental Management System for Automobiles.


This is the company that used the air-conditioning system for providing cool mist air to the passengers in a car. The Rovac air-conditioning system uses freon gas for instant cooling to the vehicle passengers. In, short this system is old but it has the efficiency to provide effective cooling and heating.

Spread the love

Leave a comment