Selective Design of an Experiment for Evaluating Air-Water Hybrid Steam Condenser for Concentrated Solar Power

In thermal power plants water-cooled steam condenser is used to reject heat from steam at the turbine outlet. In this system, makeup water of about 1500-3000 L per MWh of electricity generation is required. Therefore, in the arid places, air-cooled condensers are recommended, especially, for concentrated solar thermal power (CSP) plants. It is reported that 10 degrees C rise in air temperature reduces electricity output by about 4.2% Bustamante et al. (Appl Therm Eng xxx:1-10, 2015) [1]. For steam condensation with air at a temperature of 37 degrees C, an exergetic efficiency of the condenser is 26% in comparison to 63% for water-cooled steam condenser Blanco-Marigorta et al. (Energy, 36: 1966-1972, 2011) [2], Bustamante et al. (Appl Therm Eng xxx:1-10, 2015) [1]. Therefore, air-cooled condenser needs higher initial temperature difference (ITD) between condensing steam and air to achieve a high power output. In dry and hot places, like Rajasthan in India, during summer, air temperature reaches up to 45-50 degrees C. Whereas, condensing steam at the exit of turbine is available at a pressure of similar to 0.1 atm and at a temperature of similar to 45 degrees C. In view of this, the paper presents design of an experiment for evaluation of an air-water hybrid steam condenser. The proposed concept is based on: (a) the temperature difference between air and condensing steam in dry and arid regions and (b) achieving a high value of Nusselt/Colburn-factor to friction-factor ratio. A plate fin-and-circular tube with staggered arrangement air-cooled condenser designs is selected, as the starting point. Two possible modifications are suggested: (a) Earth (underground) for pre-cooling of ambient air or water and (b) use of water spray for additional cooling of the pre-cooled air. The obtained cold air is employed for heat transfer in condenser. In this paper, the selection and evaluation of characteristic design parameters are presented. Finally, the designed experimental setup using all these aspects is described.