geothermal power plant projects in central america - Orkustofnun

= +( − ) ( )(15)= +( − ) ( )(16)where is the specific heat of the gas and the vapor mixture that is pumped out of the condenser, andR is the ideal gas constant for the mixture. The ideal enthalpy change of the fluid when compressed toatmospheric pressure can be written as∆h = − 1 (17)Including the compressor efficiency , the demanding power for the pump can be calculated as = ( ) ∆ (18)Cooling towerIn this case, air cooling in a forced flow cooling tower is used to accommodate the heat load from thecondensing steam. A cooling tower is an evaporative heat transfer device in which atmospheric aircools warm water with direct contact between the water and the air, by evaporating part of the water(Siregar, 2004). As shown in Figure 13, the cooling water is pumped from the pond to the condenserat station 1; after this, warm water at station c2 is cooled by being sprayed into the tower where it fallsthrough; using fans at the top of the tower, an air stream is drawn into the tower at station c3, andflows out at station c4.According to Pálsson (2010) it can be assumed that the relative humidity of the outlet (c4) is 100% ifthe tower is satisfactorily large. In regards to a mixture of air and water, with their respectively molarmasses being M a and M w , the partial pressures of the air and water are defined as =∗ (19) =∗ (20)Then, taking into account the saturation pressure of water at given pressure , the relative humidity isdenoted asThe humidity ratio is defined as= (21)= ∗∗ ∗( )(22)Overall, cooling tower balance equations are formulated in order to find the required mass flow rate.Mass balance for dry air (Equation 19) and water (Equation 20) are given byAnd the energy balance equation is , = , = (23) , + , = , + , (24)h , , +h , , + h , , = h , , +h , , +h , , (25)18