Question

Steam is throttled slightly from \(2 \mathrm{MPa}\) and \(500^{\circ} \mathrm{C}\) Will the temperature of the steam increase, decrease, or remain the same during this process?

Short answer

Answer: To determine whether the temperature of the steam will increase, decrease, or remain the same during a throttling process, we must compare the initial temperature (T1) and the final temperature (T2) of the steam. If T2 > T1, then the temperature increases; if T2 < T1, then the temperature decreases; if T2 = T1, then the temperature remains the same.

Step-by-step solution

Understand throttling process

A throttling process is an adiabatic process in which steam undergoes a pressure drop without any heat or work interaction. In this process, the enthalpy of the fluid before and after the process remains the same.

Determine the initial properties of steam

Given that the initial pressure of the steam is \(2 \mathrm{MPa}\) and the temperature is \(500^{\circ} \mathrm{C}\). We can find the initial enthalpy (\(H_1\)) of the steam by referring to the steam tables for these specific values of pressure and temperature.

Determine the final properties of steam

Since the process is a throttling process, we know that the enthalpy of the steam will remain constant. Therefore, the final enthalpy of the steam after throttling, \(H_2\), will be equal to the initial enthalpy (\(H_1\)), as we determined in step 2: \(H_2 = H_1\). As the pressure of the steam has decreased after throttling, let's assume the final pressure to be \(P_2\).

Compare initial and final temperatures of steam

With the final pressure \(P_2\) and enthalpy \(H_2\), we can refer to the steam tables again to determine the final temperature of the steam, \(T_2\). By comparing the initial temperature, \(T_1\), and the final temperature, \(T_2\), after the throttling process, we can determine whether the temperature of the steam increases, decreases, or remains the same during the throttling process.

Determine the temperature change

If the final temperature \(T_2\) is greater than the initial temperature \(T_1\), then the temperature of the steam increases during the throttling process. If \(T_2\) is less than \(T_1\), then the temperature of the steam decreases during the throttling process. If \(T_2\) is equal to \(T_1\), then the temperature of the steam remains the same during the throttling process.