PhD Thesis - Energy Systems Research Unit - University of Strathclyde

- (3.12)Assuming solution saturation and considering the case of X weak , the iterative processrelies on comparing p low (the low cycle pressure calculated using the empiricalmethod explained in Section 3.3.5.1) with p weak [the low cycle pressure, in kPa,calculated as a function of solution concentration and temperature as shown inequations (3.13), (3.14) and (3.15)] until the two values converge. The coefficientsN vw in equation (3.15) are given in Table 3.7 as described by Kaita in [33].p weak = 10 LgP - (3.13)where - (3.14)where D, the dew point temperature is - (3.15)Table 3.7 - Coefficients to calculate the dew point temperaturew N 0w N 1w N 2W0 -9.133128 9.439697 x 10 -1 -7.324352 x 10 -51 -4.759724 x 10 -1 -2.882015 x 10 -3 -1.556533 x 10 -52 -5.638571 x 10 -2 -1.345453 x 10 -4 1.992657 x 10 -63 1.018418 x 10 -3 5.852133 x 10 -7 -3.924205 x 10 -8For equation (3.15), T is T 1 derived from equation (3.11), whilst X weak is varied froman initial concentration of X being equal to 40% up to a point where p weak is equal top low . Equation (3.15) is valid for a concentration X in the range of 40% to 65% [33], awide enough range to include typical working concentrations for absorption cyclechillers and ensuring no crystallisation problems occur above 65% [34]. Similarly forX strong , the same iterative process is repeated this time using T 4 , p high and p strong .Considering the solution at Point 1 and Point 6, respectively the weak solutionexiting the absorber and the strong solution entering the absorber, to be saturated, thespecific enthalpy (in kJ/kg) of Point 1 and Point 6, h 1 and h 6 , are calculated using the113