Power And Industrial Plant Engineering

Explanation
This statement is false. In a diesel engine, the fuel is ignited by the heat of compression, not by a spark plug. Diesel engines use high compression ratios to generate enough heat to ignite the fuel-air mixture without the need for a spark plug. This is in contrast to gasoline engines, which do require a spark plug to ignite the fuel-air mixture.

Explanation
In a refrigeration system, the refrigerant is in liquid state as it leaves the condenser because the condenser is responsible for removing heat from the refrigerant, causing it to condense from a high-pressure gas to a high-pressure liquid. This liquid refrigerant then flows into the expansion valve where it undergoes a pressure drop and enters the evaporator as a low-pressure liquid. Therefore, the statement is true.

Explanation
A centrifugal pump is not a positive displacement pump. It is a dynamic pump that uses centrifugal force to increase the pressure and flow of a fluid. Unlike positive displacement pumps, which trap and move a fixed amount of fluid with each cycle, centrifugal pumps use impellers to create a spinning motion that propels the fluid outward, increasing its velocity and creating a pressure differential. Therefore, the statement is incorrect, and the correct answer is False.

Explanation
Impellers for high heads usually have a low specific speed because high heads require a greater amount of energy to pump water to higher elevations. Impellers with low specific speeds are designed to operate at lower rotational speeds, allowing for higher efficiency and the ability to generate higher heads. Therefore, it is true that impellers for high heads usually have a low specific speed.

Explanation
Using a shut-off valve in the suction line of a pump is not always recommended. While it may be necessary in certain situations, such as for maintenance or repairs, it is generally advised against. A shut-off valve in the suction line can cause problems like cavitation, which can damage the pump and reduce its efficiency. It is usually better to use other methods, such as a bypass line or a control valve, to regulate the flow and pressure in the system.

Explanation
The given statement is false. A device for determining the water level in the boiler is called a water level indicator, not a steam cock. A steam cock is a valve used to control the flow of steam in a system. Therefore, the correct answer is false.

Explanation
A steam separator is a device that is specifically designed to remove moisture from steam. After steam leaves the boiler, it often contains some amount of moisture, which can cause issues in various industrial processes. The purpose of a steam separator is to efficiently separate the moisture from the steam, ensuring that the steam is as dry as possible. This helps to prevent any potential damage or inefficiencies that may occur due to the presence of moisture in the steam. Therefore, the statement "Steam separator is a device designed to remove as much as moisture as possible from steam after leaving the boiler" is true.

Explanation
The explanation for the given correct answer is that Boyle-Mariotte law states that in an isothermal condition (constant temperature), the pressure and volume of a gas are inversely proportional. This means that as the volume of a gas decreases, the pressure increases, and vice versa. This relationship holds true as long as the temperature remains constant. Therefore, the statement "In isothermal condition, Boyle-Mariotte law describes the inversely proportional relationship between the absolute pressure and volume of a gas" is true.

Explanation
Blowby does not allow the passage of water but prevents the passage of steam from the heating system.

Explanation
If the dry and wet bulb readings in air are identical, it means that the air is saturated. This is because when the air is saturated, the rate of evaporation from the wet bulb is equal to the rate of evaporation from the dry bulb, resulting in both thermometers showing the same temperature. This indicates that the air cannot hold any more moisture and is at its maximum capacity, leading to saturation.

Explanation
According to the PSME CODE 1993, water pipes should be painted green for identification.

Explanation
The given correct answer is "Deriaz type". Deriaz type water turbines have diagonal blades that are more suitable for higher heads. They are also classified as double-regulated, reaction, mixed-flow turbines.