None of the actions performed goes without loss - they are always there. The result obtained is always less than the efforts that have to be expended to achieve it. About how large the loss in performing work, and indicates the coefficient of performance (COP).
What is hidden behind this abbreviation? In fact, it is a coefficient of efficiency of a mechanism or an indicator of rational use of energy. The value of the efficiency does not have any units, it is expressed as a percentage. This coefficient is determined as the ratio of the useful work of the device to the spent on its functioning. To calculate the efficiency, the calculation formula will look like this:
EFFICIENCY = 100 * (useful work performed / work performed)
Different devices use different values to calculate this ratio. For electric motors, efficiency will look like the ratio of the useful work being done to the electrical energy received from the network. For heat engines, the efficiency will be defined as the ratio of the useful work performed to the amount of heat expended.
To determine the efficiency it is necessary that all different types of energy and work are expressed in the same units. Then it will be possible to compare any objects, such as nuclear power plants, electric power generators and biological objects, in terms of efficiency.
As already noted, due to the inevitable losses during the operation of the mechanisms, the efficiency is always less than 1. Thus, the efficiency of thermal stations reaches 90%, for internal combustion engines the efficiency is less than 30%, the efficiency of an electric transformer is 98%. The concept of efficiency can be applied both to the mechanism as a whole, and to its individual nodes. In the general assessment of the effectiveness of the mechanism as a whole (its efficiency), the product of the efficiency of the individual components of this device is taken.
The problem of efficient use of fuel did not appear today. With a continuous increase in the cost of energy resources, the issue of increasing the efficiency of mechanisms is turning from a purely theoretical into a practical one. If the efficiency of a conventional car does not exceed 30%, then we simply throw away 70% of our money spent on refueling a car.
A review of the efficiency of the internal combustion engine (internal combustion engine) shows that losses occur at all stages of its operation. So, only 75% of the incoming fuel burns out in the cylinders of the engine, and 25% is released into the atmosphere. Of all the burnt fuel, only 30-35% of the heat released is spent on useful work, the rest is either lost with exhaust gases or remains in the car’s cooling system. Of the received power, about 80% is used for useful work, the rest of the power is spent on overcoming friction and is used by auxiliary mechanisms of the car.
Even with such a simple example, an analysis of the effectiveness of the mechanism allows you to determine the direction in which work should be carried out to reduce losses. So, one of the priority areas is ensuring complete combustion of fuel. This is achieved by additional spraying of fuel and increasing pressure, which is why engines with direct injection and turbocharging are becoming so popular. The heat removed from the engine is used to heat the fuel in order to better evaporate it, and mechanical losses are reduced by using modern grades of synthetic oil.
Here we examined such a concept as a coefficient of performance, described what it is and what it affects. The effectiveness of its operation is considered on the example of an internal combustion engine and directions and ways to increase the capabilities of this device, and, therefore, efficiency, are determined.