ANS:D - all (a), (b) & (c)

Drying of a wet solid under constant drying conditions involves exposing the wet solid to specific environmental conditions to facilitate the removal of moisture. Let's break down the options:

1. Humidity: The humidity of the air surrounding the wet solid affects the rate of evaporation. If the air has a higher humidity, it contains more moisture and thus has a reduced capacity to absorb additional moisture from the solid. Conversely, if the air has lower humidity, it can absorb more moisture from the solid. Therefore, controlling the humidity of the air is crucial for effective drying.
2. Velocity: The velocity of the air passing over the wet solid influences the rate of moisture removal. Higher air velocity can enhance evaporation by carrying away the moisture-saturated air from the solid surface, promoting the diffusion of moisture from the interior of the solid to the surface. However, excessively high velocity may also lead to undesired effects such as uneven drying or damage to the solid structure.
3. Temperature: Temperature plays a fundamental role in drying processes. Increasing the temperature of the air increases its capacity to hold moisture, leading to more efficient evaporation from the wet solid. Higher temperatures also accelerate the diffusion of moisture within the solid, further facilitating drying. However, excessive temperatures can cause thermal degradation or other undesirable changes in the solid material.

So, all of the given options (humidity, velocity, and temperature) are relevant factors in the drying process under constant drying conditions. Controlling these parameters ensures consistent and efficient moisture removal from the wet solid. Therefore, the correct answer is "(d) all (a), (b), & (c)."

ANS:D - all (a), (b) & (c)

Drying of a wet solid under constant drying conditions involves exposing the wet solid to specific environmental conditions to facilitate the removal of moisture. Let's break down the options:

1. Humidity: The humidity of the air surrounding the wet solid affects the rate of evaporation. If the air has a higher humidity, it contains more moisture and thus has a reduced capacity to absorb additional moisture from the solid. Conversely, if the air has lower humidity, it can absorb more moisture from the solid. Therefore, controlling the humidity of the air is crucial for effective drying.
2. Velocity: The velocity of the air passing over the wet solid influences the rate of moisture removal. Higher air velocity can enhance evaporation by carrying away the moisture-saturated air from the solid surface, promoting the diffusion of moisture from the interior of the solid to the surface. However, excessively high velocity may also lead to undesired effects such as uneven drying or damage to the solid structure.
3. Temperature: Temperature plays a fundamental role in drying processes. Increasing the temperature of the air increases its capacity to hold moisture, leading to more efficient evaporation from the wet solid. Higher temperatures also accelerate the diffusion of moisture within the solid, further facilitating drying. However, excessive temperatures can cause thermal degradation or other undesirable changes in the solid material.

So, all of the given options (humidity, velocity, and temperature) are relevant factors in the drying process under constant drying conditions. Controlling these parameters ensures consistent and efficient moisture removal from the wet solid. Therefore, the correct answer is "(d) all (a), (b), & (c)."