Question

тепла. Каков коэффициент полезного действия двигателя?2. Рассчитайте кпд машины, если температура нагревателя 6270С, а холодильника 2270С.3. Температура нагревателя машины 1700С, холодильника 350С. Каков КПД? Как велика работа, совершаемая машиной, если от нагревателя получено 30 КДж энергии?4. Паровая машина мощностью 14,7 кВт потребляет за 1 ч работы 8,1 кг угля, удельная теплота сгорания которого 3,3 ∙ 107 Дж/кг. Определите КПД машины.5. Опишите принцип работы холодильной установки.Срочно ПОЖАЛУЙСТА

Answer 1

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Answer 2

Coefficient of Performance (COP) of an Engine

The coefficient of performance (COP) is a measure of the efficiency of an engine or a machine. It is defined as the ratio of the useful output energy or work to the input energy or work. For a heat engine, such as a car engine or a steam engine, the COP is calculated as the ratio of the desired output (work) to the input (heat energy).

Calculation of COP

To calculate the COP of a machine, we need to know the temperatures of the heat source (heater) and the heat sink (refrigerator). The COP is given by the formula:

COP = (Temperature of the heater - Temperature of the refrigerator) / Temperature of the heater

Let's calculate the COP for the given temperatures:

1. Temperature of the heater = 62°C = 62 + 273 = 335 K Temperature of the refrigerator = 22°C = 22 + 273 = 295 K

COP = (335 - 295) / 335 = 0.1194

2. Temperature of the heater = 170°C = 170 + 273 = 443 K Temperature of the refrigerator = 35°C = 35 + 273 = 308 K

COP = (443 - 308) / 443 = 0.3049

Calculation of Work Done by the Machine

To calculate the work done by the machine, we need to know the amount of energy obtained from the heater. The work done by the machine is given by the formula:

Work = Energy obtained from the heater - Energy rejected to the refrigerator

Let's calculate the work done by the machine for the given energy:

Energy obtained from the heater = 30 kJ

Work = 30 kJ - Energy rejected to the refrigerator

Unfortunately, the information about the energy rejected to the refrigerator is not provided, so we cannot calculate the exact work done by the machine.

Calculation of COP for a Steam Engine

To calculate the COP of a steam engine, we need to know the power output and the amount of coal consumed. The COP is given by the formula:

COP = Power output / Energy input

Let's calculate the COP for the given information:

Power output = 14.7 kW Amount of coal consumed = 8.1 kg Specific heat of combustion of coal = 3.3 * 10^7 J/kg

Energy input = Amount of coal consumed * Specific heat of combustion of coal

Energy input = 8.1 kg * 3.3 * 10^7 J/kg = 2.673 * 10^8 J

COP = Power output / Energy input = 14.7 kW / 2.673 * 10^8 J = 5.5 * 10^-5

Principle of Operation of a Refrigeration System

A refrigeration system, such as a refrigerator or an air conditioner, operates based on the principle of heat transfer. It uses a working fluid, typically a refrigerant, to absorb heat from a low-temperature environment (the refrigerator) and reject it to a high-temperature environment (the surroundings).

The principle of operation involves the following steps:

1. Compression: The refrigerant is compressed, which increases its pressure and temperature. 2. Condensation: The high-pressure, high-temperature refrigerant is cooled down and condensed into a liquid state by rejecting heat to the surroundings. 3. Expansion: The high-pressure liquid refrigerant is passed through an expansion valve, where it undergoes a pressure drop, resulting in a decrease in temperature. 4. Evaporation: The low-pressure, low-temperature refrigerant absorbs heat from the low-temperature environment, causing it to evaporate and turn into a gas. 5. Repeat: The gaseous refrigerant is then compressed again, and the cycle continues.

This continuous cycle of compression, condensation, expansion, and evaporation allows the refrigeration system to transfer heat from a low-temperature environment to a high-temperature environment, thereby cooling the desired space.

I hope this information helps! Let me know if you have any further questions.