How does the thermal efficiency of an ideal cycle, in general, compare to that of a Carnot cycle operating between the same temperature limits? The Carnot cycle have the maximum thermal efficiency of all heat engines operating between the same temperature limits.

Reversible processes produce the maximum amount of work If a process does work on the surroundings, you get more work out of the process if it is done slowly. This is because less heat is lost to the surroundings. So a reversible process (infinitely slow) does the maximum work.

No actual heat engine operating at same temperatures limits produces more efficiency than Carnot heat engine.

The Carnot cycle consists of the following four processes:

• A reversible isothermal gas expansion process.
• A reversible adiabatic gas expansion process.
• A reversible isothermal gas compression process.
• A reversible adiabatic gas compression process.

According to the second law of thermodynamics, however, it cannot convert *all* of the heat energy supplied to it into work. Basic heat engine: hot reservoir, cold reservoir, and a machine to convert heat energy into work. This is a simplified diagram of a heat engine, along with its thermal cycle.

Any engine using the Carnot cycle, which uses only reversible processes (adiabatic and isothermal), is known as a Carnot engine. Any engine that uses the Carnot cycle enjoys the maximum theoretical efficiency.

In the reverse Carnot cycle, work is done to extract heat from one system and expel it into another via four processes, two isothermal and two isentropic . In process 1→2, the gas is isentropically compressed, and there is no heat flow into or out of the refrigerator. In process 3→4, the gas is isentropically expanded.

Carnot’s theorem states that all heat engines between two heat reservoirs are less efficient than a Carnot heat engine operating between the same reservoirs. Every Carnot heat engine between a pair of heat reservoirs is equally efficient, regardless of the working substance employed or the operation details.

These assumptions are: (1)The working fluid is air, which continuously circulates in a closed loop and always behaves as an ideal gas. (2)All the processes are internally reversible. (3)The combustion process is replaced by a heat addition process. (4)The exhaust process is replaced by a heat rejection process.

However, you cannot cool the kitchen by having the refrigerator door open. The refrigerator exhausts more heat than it removes from the refrigerated volume, so the room actually gets warmer with the refrigerator door open.

According to electricity expert Michael Bluejay, the average refrigerator uses 488 BTUs per hour in normal use.

If a refrigerator’s door is kept open, then room will become hot, because then refrigerator exhaust more heat into the room than earlier. In this way, temperature of the room increases and room becomes hot. No refrigerator is efficient. Thus it exhaust more heat into the room than it extract from it.

A refrigerator is transporting heat from the inside cavity to the outside. It is also running an irreversible process, the energy dissipates out as heat and work (mostly heat), making the net temperature of the room increase.

When you open your refrigerator, the cold air that keeps your food fresh escapes and is replaced by warm air from the room. Your refrigerator’s compressor has to then drive the warm air out and bring the temperature back to normal, elevating not only your monthly energy bill, but also your environmental footprint.

Refrigerators work by causing the refrigerant circulating inside them to change from a liquid into a gas. This process, called evaporation, cools the surrounding area and produces the desired effect. When you release the contents into the lower pressure open space, it turns from a liquid to a gas.

9 Ways to Make Your Refrigerator More Efficient

1. Take Its Temperature. Check the temperature of your refrigerator and freezer with a thermometer.
2. Clean the Coils. Clean the condenser coils at least once a year.
3. Don’t Forget to Defrost.
4. Regulate Room Temperature.
5. Sweat & Save.
6. Make Room.
7. Test the Seals.
8. Practice Smart Habits.

An evaporator fan located above or below the evaporator coils blows the cold air, circulating it through the freezer to keep foods frozen. A small vent in the wall of the freezer allows the cold air to pass into the refrigerator compartment, keeping the fresh food compartment cool.