. Thermodynamics and heat transfer

1.1 Calculation of thermodynamic cycle

Figure 2 presents the scheme of thermodynamic cycle of a typical dry fluid. Point 1 illustrates the state of fluid at the condenser outlet; Point 2 at the Pump 1 outlet; Point 2′ at the regenerator outlet; Point 3 at the FPC collectors outlet; Point 4 at the evaporator outlet (on the normal condition of irradiation); and Point 5 at the turbine outlet. The points being referred to in Fig. 2 are placed in Fig. 1 with circles outside the numbers (with the exception of 2′). The reversible process of pressurization or expansion are described by 2 s or 5s respectively. Formulas for heat transfer and power conversion are developed below. Enthalpy at Point 2′ is calculated by the following:

h2′ = h2 + [h5 -(T6 =t2 )] • Er (1)

Where er is the regenerator efficiency. Enthalpy at Point 6 is assigned by assuming T6 = T2 . Total heat transferred to organic fluid from the collectors is calculated by the following:

Q = К – hr (2)

Power generated by the turbine (Eq.3) and that consumed by Pump 1 (Eq.4) are calculated by the following:

Ю LO 1 1

II ІдГ

ы II

(3)

1 = (h2 h1)

:V1( P2 – Р1)/Пр

(4)

Meanwhile, net power is calculated by the following:

Wore = Wt •Eg – Wp,1 – Wp,2 (5)

In case the negative effect of Pump 2 is considered, calculation of required power Wp 2 is presented in the following section. Practical ORC efficiency is calculated by the following:

Q


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Fig. 2. Thermodynamic cycle of a typical dry fluid

 

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