lookisurfer.blogg.se - Net workdone in brayton cycle

The heat is absorbed from the low-temperature reservoir, heat in the high-temperature reservoir is rejected, and a work input is needed to achieve all this. This time, the cycle remains the same but the directions of heat and work interactions are reversed. That is all the processes that form can be reversed, in which case it becomes the Carnot refrigeration cycle. The Carnot cycle heat-engine can be called as a fully reversible cycle.

However, such an imaginary engine is used as the ultimate standard pf comparison of all heat engines.

Thus, it is difficult to realise Carnot’s engine in actual practice.

It is difficult to eliminate friction between the multiple moving parts of the engine, and also heat losses due to conduction, radiation, etc.

We know that sudden change s in the speed of an engine is not possible in actual practice.

But adiabatic expression 2-3 and adiabatic compression 4-1 should be carried out as quickly as possible, in order to approach ideal adiabatic conditions.

Thus, the isothermal compression 3-4 will have to be taken out very slow.

The reason for the same is that the isothermal expansion 1-2 will have to be carried out very slow to ensure that the air is always at temperature T1.

It can be noted that it is difficult to make the engine working on Carnot’s cycle.

∴ Heat supplied = Work done during isothermal expansion

The heat supplied the hot body is fully absorbed by the air and is utilized in doing external work.

This isothermal expansion is represented by curve 1-2 on p-v and T-s diagrams in the figure.

It means that the temperature T2 (at point 2) equals to the temperature T1.

The air expands, practically at constant temperature T1, from v1 to v2.The source (hot body, H.B) at a higher temperature is brought in contact with the bottom B of the cylinder.Isentropic Compression Process 1-2 Isothermal Expansion.At this point, let p1, T1, and v1 be the pressure, temperature, and volume of the air, sequentially. Let the engine cylinder contain m kg of air at its original condition represented by point 1 on the p-v and T-s diagrams. Now, let us consider the four stages of Carnot’s cycle. Read also: The rmodynamic Cycle: Its Classification, Working, Terms Used in Thermodynamics and More. One at a higher temperature and the other at a lower temperature. The engine is assumed to work between two sources of infinite capacity.

However, the bottom B of the cylinder can be covered, at will, by an insulating cap I.C. But the bottom B of the cylinder is a perfect conductor of heat. The walls of the cylinder and piston are perfect non-conductors of heat. The engine developed by Carnot has air (which is assumed to work as a perfect gas) as its working substance enclosed in a cylinder, in which a frictionless piston A moves. In a Carnot cycle, the working substance is subjected to a cyclic operation consisting of two isothermal and two adiabatic processes. He focussed his attention to the basic features of a heat engine. This cycle is designed by “ Carnot” who was the first scientist to analyze the problem of the efficiency of a heat engine, ignoring its mechanical details.