Heat/Pressure Loss in Regulator Valve

The flow of steam through stop valve or regulator valve is accompanied by heat loss due throttling process. This heat loss is called as heat loss in regulator valve.  The pressure inlet steam (P₀) to turbine generator is usually reduced so initial pressure inlet steam (P₀’) less than before. Initial pressure drop (Δ P₀) is estimated at 3% - 5 % of P₀. If the loss is assumed as 5% so the pressure inlet steam to turbine generator can be expressed as follow:

ΔP = P₀ - P₀’

ΔP = 5% P₀

The energy loss in regulator valve is determine by equation below

Δh = h₀ - h₀’

Where:

h₀         = reduction in total calorific value of turbine

Calorific value will decrease after experiencing the pressure drop due to setting through regulator valve or stop valve. The losses occurred in valve can be seen in the figure below.

Figure 1: Expansion Steam and Losses in Valve

Caption:

H_n        = Losses in nozzle

H_b        = loss on the blade motion

H_c        = loss due to exit velocity

P₀         = pressure inlet steam to turbine

P₀’       = pressure steam before entering nozzle

P₂         = pressure outlet steam from turbine

H₀        = decrease in heat

H₀’       = theoretical decrease in heat

H_i        = decrease in heat which is utilized in turbine