Derived thermodynamic design data for heat pump systems operating on R170

Heat Recovery Systems & CHP Vol. 11, No. 2/3, pp. 103-111, 1991 Printed in Great Britain

0890-4332/91 $3.00+ .00 Pergamon Press pie

THERMODYNAMIC DESIGN DATA FOR ABSORPTION HEAT PUMP SYSTEMS OPERATING ON AMMONIA-LITHIUM NITRATE--PART TWO. HEATING R. BEST,W. RIVERA,I. PILATOWSKY and F. A. HOLLAND* Laboratorio de Energia Solar de la UNAM, Apartado Postal 34, 61580, Temixco, Morelos, M6xico, and *Department of Chemical and Gas Engineering, University of Salford, Salford M5 4WT, U.K. (Received 11 April 1990) Abstract--The free choice of operating temperatures in absorption systems is limited by the Gibbs phase rule and the thermodynamic properties of the working pair. Tables of possible combinations of operating temperatures and concentrations, including flow ratios, Carnot coefficients of performance and enthalpy. based coefficients of performance have been presented for ammonia-lithium nitrate absorption systems for heating. The interactions of operating temperatures have been illustrated graphically.

NOMENCLATURE

(COP)

(eR) H M P

Q T X

coefficient of performance (dimensionless) flow ratio (dimensionless) enthalpy per unit mass [kJ kg -~] mass flow rate [kg s -t ] pressure [bar] heat load [kW] temperature [°C] weight [%]

Subscripts Ab absorber AH actual for heating Am ammonia CH Carnot for heating Co condenser EH enthalpy for heating Ev evaporator Ge generator H heating S solution

INTRODUCTION

A conventional heat driven absorption heat pump basically consists of an evaporator, a condenser, a generator and an absorber as shown in Fig. 1. The choice of the designer in the selection of the four basic operating temperatures TEv, TAb, Tco and TGe is limited by the Gibbs phase rule. For an absorption system with two components and two phases, the number of degrees of freedom is two. If two of the operating variables are chosen as the free variables then the other conditions are determined by the thermodynamic equilibrium data for the working pair. The flow ratio (FR) is the ratio of the mass flow rate of solution to the mass flow rate of pure refrigerant in the primary circuit linking the condenser and the evaporator as defined by Eisa et al. [1]. This can be written as MAb

(v~) = ~-~.

O)

Alternatively, it can be rewritten in terms of concentrations as XAm -- XC~

(FR) = X^b - Xoc' ~Rs uu/2/3-A

103

(2)

104

R. BESTet al.

~oo~ coo~,~

Geoerotor ( ~ QG~

~--

Solution pump

~ Exp~n~ionvalve z

2

I

I

Fig. I. Simplified b l ~ k diagram for a basic abso~tion heat pump.

where XAb is the weight per cent of ammonia in the solution entering the generator from the absorber, and Xoe and XA~ are the corresponding concentrations of ammonia in the streams leaving the generator for the absorber and condenser respectively. In this work the data have been correlated using equations (1) and (2) for the case of pure ammonia entering the condenser XAm= 1.0

IDEAL COEFFICIENT OF PERFORMANCE OF AN ABSORPTION HEAT PUMP The coefficient of performance of an absorption heat pump is equal to the heat load in the absorber and condenser per unit heat load in the generator. (COP)AH =

QAb + Qco Qoe

(3)

From thermodynamic, mass and heat balance considerations and referring to Fig. 1, it can be shown [2] that (COP)c~ = 1 + L \

T~e

./1 / \ T. c o - TEv/~

(4)

and

(COP)E. =

HI -F (FR - l ) n 4 - ( F R ) H 5 + H6 - H8 , n 6 H- (FR -- 1)H4 - ( F R ) H 5

(5)

where (COP)cu is the Carnot coefficient of performance for the system and is dependent only on the four basic temperatures TEv, TAb, Tco and Toe, and (COP)E~ is the enthalpy based coefficient of performance for heating.

THERMODYNAMIC

PROCESS

DESIGN

DATA

The theoretical Carnot coefficient of performance (COP)cH, the enthalpy based coefficient of performance (COP)EH, the concentration of the solution in the absorber and the generator, and the flow ratio have been calculated for the ammonia-lithium nitrate system for the following range of temperatures: (1) evaporator temperatures from 20°C to 50°C in 10°C increments at absorber temperatures of 50°C-100°C in 10°C increments;

Data for absorption heat pump s y s t e m s ~ I I

105

and (2) generator temperatures from 90°C to 170°C in 10°C increments at condenser t~nperatures from 50°C to 70°C in 10°C increments. Equation (4) has been used for the calculation of the Carnot coefficient of performance. Equation (5) has been used for the calculation of the enthalpy based coefficient of performance. Equation (2) was used to calculate the flow ratio. The concentrations of ammonia in the absorber XAb and the generator Xoc and the enthalpies at different state points were calculated using the thermodynamic data of Infante Ferreira [3]. Tables 1-10 list some of the design data for each combination of the four basic operating temperatures.

Table 1. Derived thermodynamic design data for absorption systems operating on

ammonia-lithium nitrate for heating

TE~

r,,b

~o

rc~

x~b

xc~

(Fa)

(cov)c.

(cov)~.

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 60 60 60 60 60

50 50 50 50 50 50 50 60 60 60 60 60 60 60 70 70 70 70 70 70 70 50 50 50 50 50

90 I00 II0 120 130 140 150 I00 IlO 120 130 140 150 160 ll0 120 130 140 150 160 170 100 110 120 130 140

54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 54.37 49.46 49.46 49.46 49.46 49.46

50.07 45.97 42.32 38.99 35.90 33.01 30.27 50.17 46.11 42.48 39.18 36.11 33.23 30.51 50.22 46.20 42,60 39,32 36,28 33,41 30,70 45.97 42,32 38,99 35.90 33.01

11.62 6.43 4.79 3.97 3.47 3.14 2.89 II.87 6.52 4.84 4.00 3.50 3.16 2.91 12.00 6.58 4.88 4.03 3.52 3.18 2.93 15.48 8.07 5.83 4.73 4.07

2.076 2.309 2.530 2.740 2.939 3.128 3.309 1.982 2.148 2.305 2.454 2.596 2.732 2.861 1.918 2.0~4 2.163 2.277 2.385 2.489 2.587 2.047 2.275 2.491 2.696 2.892

1.346 1.415 1.435 1.441 1.441 1.438 1.434 1.286 1,363 1-389 1.399 1.403 1.402 1.400 1.240 1.318 1.348 1.361 1.367 1.369 1.368 1.294 1.372 1.399 1.408 1,411

Table 2. Derived thermodynamic design data for absorption systems operating on

ammonia-lithium nitrate for heating TEv

TAb

Tco

Tc,e

X^b

Xc,e

(FR)

(cOe)cr ~

(COP)E.

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

60 60 60 60 60 60 60 60 60 60 60 60 60 70 70 70 70 70 70 70 70 70 70 70 70 70

50 60 60 60 60 60 60 70 70 70 70 70 70 50 50 50 50 50 60 60 60 60 60 70 70 70

150 ll0 120 130 140 150 160 120 130 140 150 160 170 ll0 120 130 140 150 120 130 140 150 160 130 140 150

49.46 49.46 49.46 49.46 49.46 49.46 49.46 49.46 49.46 49.46 49.46 49.46 49.46 45.25 45.25 45.25 45.25 45.25 45.25 45.25 45,25 45.25 45.25 45.25 45.25 45.25

30,27 46.11 42.48 39,18 36,11 33.23 30.51 46.20 42.60 39.32 36.28 33.41 30.70 42.32 38.99 35.90 33.01 30.27 42.48 39.18 36.11 33.23 30.51 42.60 39.32 36.28

3.63 16.07 8.24 5.91 4.79 4.11 3.67 16.49 8.37 5.98 4.83 4.15 3.69 19.65 9.74 6.85 5.47 4.65 20.77 10.01 6.99 5.55 4.71 21.66 10.23 7.10

3.078 1.956 2.118 2.272 2.419 2.559 2.692 1.895 2.018 2.135 2.247 2.353 2.455 2.020 2.243 2.454 2.655 2.847 1.932 2.091 2.242 2.385 2.523 1.872 1.993 2.108

1.411 1.237 1.320 1.352 1.367 1.373 1.375 1.194 1.276 1.312 1.329 1.338 1.342 1.254 1.338 1.369 1.382 1.387 1.199 1.287 1,323 1.341 1.349 1.159 1.244 1.283

R. BEST et al.

106

Table 3. Derived thermodynamic design data for absorption systems operating on ammonia-lithiumnitrate for heating TEv

TAb

Tco

T~

X,~b

Xc~

20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20

70 70 80 80 80 80 80 80 80 80 80 80 80 80 90 90 90 90 90 90 90 90 90 I00 I00 100

70 70 50 50 50 50 60 60 60 60 70 70 70 70 50 50 50 60 60 60 70 70 70 50 50 60

160 170 120 130 140 150 130 140 150 160 140 150 160 170 130 140 150 140 150 160 150 t60 170 140 150 150

45,25 45.25 41.52 41.52 41.52 41.52 41.52 41,52 41.52 41.52 41.52 41.52 41.52 41.52 38.12 38.12 38.12 38.12 38.12 38.12 38.12 38.12 38.12 34.97 34.97 34.97

33.41 30,70 38.99 35.90 33.01 30,27 39.18 36.11 33.23 30.51 39.32 36.28 33.41 30.70 35.90 33.01 30.27 36.11 33,23 30.51 36.28 33.41 30.70 33.01 30.27 33.23

(FR) 5.62 4.76 24.13 11.42 7.87 6.20 26.01 11.82 8.06 6.31 27.66 12.16 8.22 6.41 28.95 13,11 8.88 31.87 , 13.68 9.13 34,62 14.16 9.35 34.11 14.82 38.41

(COP)c.

(COP)~..

2.218 2.323 1.994 2.212 2.419 2.616 1.909 2.064 2.212 2.353 1.851 1.970 2.083 2.191 1.969 2.182 2.385 1.887 2.039 2.184 1.831 1.947 2.058 1.946 2.154 1.866

1.303 1.315 1,222 1.310 1.344 1.360 1.169 1.260 1.299 1.319 1.131 1.218 1,260 1.282 1.196 1.287 1,324 1.145 1.237 1.279 1.110 1.197 1,241 1.174 1.268 1.125

DISCUSSION OF THERMODYNAMIC PROCESS DESIGN DATA Figure 2 shows the variations of the coefficients of performance and flow ratio with generator temperature at absorber temperatures of 80°C, 90°C and 100°C respectively. It can be seen that the Carnot coefficient of performance increases with generator temperature. The enthalpy based coefficient of performance increases with temperature to a peak value and then remains almost constant. The value of the flow ratio decreases as the generator temperature is increased. The values of the coefficients of performance are higher at the lower absorber temperatures. Figure 3 shows the variation of the coefficients of performance and flow ratio with condenser temperature at three different absorber temperatures. It can be seen from Fig. 3 that the coefficients of performance decrease while the flow ratio increases with an increase in condenser temperature. Table 4. Derived thermodynamic design data for absorption systems operating on ammonia-lithium nitrate for heating

TEv

T,~b

TCo

TGo

X~b

~,

(FR)

20 20 20 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30

100 100 100 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 60 70 70

60 70 70 50 50 50 50 50 50 50 60 60 60 60 60 60 60 70 70 70 70 70 70 70 50 50

160 160 170 90 100 I10 120 130 140 150 100 110 120 130 140 150 160 110 120 130 140 150 160 170 100 110

34.97 34.97 34.97 54.59 54.59 54,59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54.59 54,59 49,72 49.72

30.51 33.41 30.70 50.07 45.97 42.32 38.99 35.90 33.01 30.27 50.17 46,11 42,48 39.18 36.11 33.23 30.51 50.22 46.20 42.60 39.32 36.28 33.41 30.70 45.97 42.32

15.56 42.73 16.22 11.06 6.27 4.70 3.91 3.43 3.10 2.87 11.29 6.36 4.75 3,95 3.46 3.13 2.89 11,40 6.41 4.79 3.98 3.48 3.14 2.90 14.41 7.79

(CO~')c. 2.015 1.812 1,926 2.252 2.625 2.978 3.313 3.632 3.935 4.223 2.083 2.319 2.542 2.754 2,956 3.149 3.333 1.989 2.156 2.316 2.467 2.612 2.749 2.881 2.218 2.582

(COP)E. 1.219 1.092 1.180 1.412 1.464 1.476 1.476 1.471 1.465 1.459 1.337 1.404 1.424 1.430 1.430 1.427 1.423 1.280 1.352 1.378 1.388 1.391 1,391 1.389 1.361 1.423

D a t a for absorption heat pump s y s t e m s - - I I

107

Table 5. D~dved thermodynamic design data for absorption systems operating on

Tv.v

T^b

Tc~

30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30

70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 80 80 80 80 80 80 80 80 80 80

50 50 50 50 60 60 60 60 60 60 70 70 70 70 70 70 50 50 50 50 50 60 60 60 60 60

ammonia-lithium nitrate for heating Toe X^b Xoe (FR) (COP)ca (COP)v.n 120 130 140 150 II0 120 130 140 150 160 120 130 140 150 160 170 llO 120 130 140 150 120 130 140 150 160

49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 49.72 45.55 45.55 45.55 45.55 45.55 45,55 45.55 45.55 45.55 45.55

38.99 35.90 33.01 30.27 46.11 42.48 39.18 36.11 33.23 30.51 46.20 42.60 39.32 36.28 33.41 30.70 42.32 38.99 35.90 33.01 30.27 42.48 39.18 36.11 33.23 30.51

5,68 4.64 4.01 3.58 14.92 7.95 5.77 4.69 4.05 3.62 15.27 8.07 5.83 4.74 4.08 3.64 17.86 9.30 6.65 5.34 4.56 18.78 9.55 6.77 5.42 4.62

2.927 3.256 3.568 3.865 2.055 2.285 2.504 2.712 2.910 3.099 1.964 2.128 2.284 2.433 2.574 2.710 2.187 2.542 2.880 3.201 3.507 2.028 2.253 2.467 2.671 2.866

1.440 1.443 1.442 1.438 1.287 1.362 1.388 1.398 1.401 1.400 1.233 1.311 1.342 1.356 1.362 1.365 1.321 1.390 1.411 1.418 1.419 1.249 1.329 1.359 1.372 1.377

The rate of decrease in (COP)EHis higher at higher condenser temperatures. The sensitivity of the decrease in (COP)EHis also greatest at the higher absorber temperature. The rate of increase in flow ratio is higher for higher absorber temperatures. Figure 4 shows the variation of coefficient of performance and flow ratio with evaporator temperature at three different absorber temperatures. It can be seen from Fig. 4 that the coefficients of performance increase while the flow ratio decreases with an increase in evaporator temperature. The rate of decrease in flow ratio is higher at higher absorber temperatures.

Table 6. Derived thermodynamic design data for absorption systems operating on TEv

T^b

Tco

30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30

80 80 80 80 80 90 90 90 90 90 90 90 90 90 90 90 90 100 100 100 100 100 IO0 100 100 100

70 70 70 70 70 50 50 50 50 60 60 60 60 70 70 70 70 50 50 50 60 60 60 70 70 70

ammonia-lithium nitrate for heating Toe X^b Xoe (FR) (COP)c~ (COP)Eu 130 140 150 160 170 120 130 140 150 130 140 150 160 140 150 160 170 130 140 150 140 150 160 150 160 170

45.55 45.55 45.55 45.55 45.55 41.84 41.84 41.84 41.84 41.84 41.84 41.84 41.84 41.84 41.84 41.84 41.84 38.46 38.46 38.46 38.46 38.46 38.46 38.46 38.46 38.46

42.60 39.32 36.28 33.41 30.70 38.99 35.90 33.01 30.27 39,18 36.11 33.23 30.51 39.32 36.28 33.41 30.70 35.90 33.01 30.27 36.11 33.23 30.51 36.28 33.41 30.70

19.51 9.75 6.87 5.49 4.67 21.42 I0.80 7.59 6.03 22.88 11.16 7.76 6.13 24.13 I 1.46 7.91 6.22 25.07 12.29 8.51 27,22 12.78 8.74 29.18 13.20 8.93

1.940 2.100 2.254 2.400 2.539 2.156 2,504 2.834 3.149 2.002 2.223 2.433 2.633 1.917 2.074 2.225 2.368 2.128 2.467 2.791 1.978 2.194 2.400 I. 895 2.050 2.197

1.197 1.278 1.313 1.330 1.339 1.290 1.362 1.387 1.396 1.281 1.302 1.335 1.350 1.169 1.252 1.290 1.309 1.263 1.340 1.367 1.194 1,279 1.315 1.146 1.231 1.271

R. BEST et al.

108

Table 7. Derived thermodynamic design data for absorption systems operating on

ammonia-lithium nitrate for heating

TE~

TAb

Tco

T~,

X/~,b

Xc~

(FR)

(COP)cn

(COP)~.n

40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40

70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 80 80 80 80 80

50 50 50 50 50 50 50 60 60 60 60 60 60 60 70 70 70 70 70 70 70 50 50 50 50 50

90 100 110 120 130 140 150 100 110 120 130 140 150 160 110 120 130 140 150 160 170 100 110 120 130 140

54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 54.74 49.92 49.92 49.92 49.92 49.92

50.07 45.97 42.32 38.99 35.90 33.01 30.27 50.17 46.11 42.48 39.18 36.11 33,23 30,51 50,22 46.20 42.60 39.32 36.28 33.41 30.70 45.97 42.32 38.99 35.90 33.01

10.69 6.16 4.64 3.87 3.40 3.08 2.85 10.90 6.24 4.69 3.91 3.43 3.10 2.87 11.01 6.30 4.73 3.93 3.45 3.12 2.88 13.67 7.58 5.58 4.57 3.96

2.725 3.517 4.269 4.982 5.660 6.305 6.920 2.259 2.634 2.991 3.330 3.653 3.960 4.253 2.090 2.327 2.553 2.768 2.973 3.169 3.355 2.678 3,452 4.186 4.883 5.547

1.499 1.524 1.522 1.515 1.505 1.496 1.487 1.401 1.453 1.464 1.464 1.460 1.455 1.448 1.328 1.392 1.412 1.418 1.418 1.416 1.412 1.451 1.485 1.488 1.483 1.477

THE IMPORTANCE OF DERIVED THERMODYNAMIC DATA In absorption systems, the coefficient of performance is a measure of the system efficiency. The flow determines the size of the various items of equipment. An increase in the flow ratio affects the performance in the following ways: (i) the concentration difference between the absorber and generator is decreased; (ii) the load on the economizer, normally placed between the absorber and generator is increased [4], [5]; (iii) the heat losses from the system could be higher; (iv) the power required for the solution pump will increase.

Table 8. Derived thermodynamic design data for absorption systems operating on

ammonia-lithium nitrate for heating TEv

T~,b

Tco

T~

X~,b

Xc~

(FR)

(COP)c,

(COP)eH

40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 90 40 40 40 40 40 40 40 40 40 40

80 80 80 80 80 80 80 80 80 80 80 80 80 90 90 50 90 90 90 90 90 90 90 90 90 90

50 60 60 60 60 60 60 70 70 70 70 70 70 50 50 50 50 50 60 60 60 60 60 70 70 70

150 110 120 130 140 150 160 120 130 140 150 160 170 110 120 130 140 150 120 130 140 150 160 130 140 150

49.92 49.92 49.92 49.92 49.92 49.92 49.92 49.92 49.92 49.92 49.92 49.92 49.92 45.79 45.79 45.79 45.79 45.79 45.79 45.79 45.79 45.79 45.79 45.79 45.79 45.79

30.27 46.11 42.48 39.18 36.11 33.23 30.51 46.20 42.60 39.32 36.28 33.41 30.70

3.55 14.12 7.73 5.66 4.63 4.00 3.58 14.44 7.84 5.72 4.67 4.03 3.60 16.64 8.98 6.49 5.24 4.49 17.42 9.21 6.60 5.32 4.55 18.04 9.39 6.70

6.180 2.226 2.593 2.942 3.274 3.590 3.891 2.062 2.294 2.516 2.727 2.928 3.120 2.634 3.389 4.107 4.789 5.440 2.195 2.553 2.895 3.220 3.530 2,036 2.263 2.480

1.469 1.351 1.412 1.428 1.432 1.431 1.428 1.280 1.351 1.376 1.386 1.389 1.389 1.414 1.453 1.460 1.458 1.454 1.313 1.379 1.400 1.407 1.408 1.243 1.319 1.348

42.32 38.99 35.90 33.01 30.27 42.48 39.18 36.11 33.23 30.51 42.60 39.32 36.28

109

Data for absorption heat pump s y s t e m s - - I I Table 9. Derived thermodynamic design data for absorption systems operating on

ammonia-lithium nitrate for heating

TEv

TAb

~Co

~e

~Ab

~(~

(FR)

40 40 40 40 40 40 40 40 40 40 40 40 40 40 50 50 50 50 50 50 50 50 50 50 50

90 90 I00 100 I00 100 lO0 lO0 lO0 100 lO0 lO0 I00 I00 80 80 80 80 80 80 80 80 80 80 80

70 70 50 50 50 50 60 60 60 60 70 70 70 70 60 60 60 60 60 60 60 70 70 70 70

160 170 120 130 140 150 130 140 150 160 140 150 160 170 100 II0 120 130 140 150 160 II0 120 130 140

45.79 45.79 42.10 42.10 42.10 42.10 42.10 42.10 42.10 42.10 42.10 42.10 42.10 42.10 54.84 54.84 54.84 54.84 54.84 54.84 54.84 54.84 54.84 54.84 54.84

33.41 30.70 38.99 35.90 33.01 30.27 39.18 36.11 33.23 30.51 39.32 36.28 33.41 30.70 50.17 46.11 42.48 39.18 36.11 33.23 30.51 50.22 46.20 42.60 39.32

5.38 4.59 19.59 I0.34 7.37 5.89 20.80 10.66 7.53 5.99 21.82 10.94 7.66 6.08 10.67 6.17 4.65 3.88 3.41 3.09 2.86 I0.78 6.22 4.69 3.91

(COP)cn (COPh. 2.687 2.884 2.593 3.330 4.031 4.700 2.165 2.516 2.850 3.169 2.010 2.233 2.446 2.649 2.732 3.530 4.288 5.007 5.692 6.345 6.968 2.265 2.644 3.004 3.346

1.361 1.366 1.383 1.427 1.437 1.438 1.282 1.352 1.376 1.386 1.214 1.292 1.325 1.340 1.486 1.512 1.511 1.504 1.495 1.485 1.476 1.389 1.440 1.452 1.453

For the same value of the coefficient of performance, the flow ratio will be different from one working pair to another. For working pairs for which the thermodynamic and thermophysical data are available, the correlation between the operating temperatures together with the theoretical coefficients of performance and the flow ratios presented in this work will also help the process design engineer in the choice of items of equipment and their sizing, especially for the economizer heat exchanger. The data presented will provide information on the effect on efficiency due to changes in operating conditions and information on possible combinations and operational limits of temperatures for the ammonia-lithium nitrate system.

Table 10. Derived thermodynamic design data for absorption systems operating on

ammonia-lithium nitrate for heating TEv

TAb

Tco

Tc~

X^b

XCk

(FR)

(COP)ca

(COP)r.,

50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50

80 80 80 90 90 90 90 90 90 90 90 90 90 90 90 100 100 I00 I00 I00 I00 100 I00 100 100

70 70 70 60 60 60 60 60 60 70 70 70 70 70 70 60 60 60 60 60 70 70 70 70 70

150 160 170 110 120 130 140 150 160 120 130 140 150 160 170 120 130 140 150 160 130 140 150 160 170

54.84 54.84 54.84 50.07 50.07 50.07 50.07 50.07 50.07 50.07 50.07 50.07 50.07 50.07 50.07 45.97 45.97 45.97 45.97 45.97 45.97 45.97 45.97 45.97 45.97

36.28 33.41 30.70 46.11 42.48 39.18 36.11 33.23 30.51 46.20 42.60 39.32 36.28 33.41 30.70 42.48 39.18 36.11 33.23 30.51 42.60 39.32 36.28 33.41 30.70

3.43 3.11 2.87 13.59 7.58 5.58 4.58 3.96 3.55 13.88 7.68 5.64 4.62 4.00 3.58 16.49 8.95 6.48 5.24 4.49 17.05 9.13 6.57 5.30 4.54

3.673 3.984 4.281 2.687 3.466 4.206 4.910 5.582 6.222 2.233 2.603 2.955 3.291 3.611 3.916 2.644 3.404 4.128 4.818 5.476 2.202 2.564 2.909 3.238 3.552

1.449 1.444 1.438 1.439 1.473 1.477 1.473 1.466 1.459 1.341 1.400 1.417 1.421 1.420 1.417 1.402 1.442 1.449 1.448 1.444 1.304 1.368 1.389 1.396 1.397

110

R. BEST

et al.

(sse'~uo!sue~u!p) '(~1_-I) o!),oa ~oI..4 ~

-=

-~

£

-~

-

o~

~-

=~

8

~;~_

=o~

,,_

-£

ii

O

e

7

-8

, , ~ ~

~

,,

_

,~

~

..~

p

~

~=

~

-

I

I

~o

I

Q ~

I^I

o ~i

I

~Q " , ~ -:

i I I ~ ~

=o

I

~-:

I

_m,

m "~

(~e'luolsueuJfp) =H:~(cJO3 ) pUO HO(dO3 ) eououJJotJltd ~io ~ue!o!~l~.eo 3

(sse-luo!$u~uJ!p) '(~1-1) o!),oJ ~o1-1

~

~

£~

~

")T •

~~

~=

~~

~

~

I

~

I

~

I

,,,

~,~~

,

N

/l//'//

.

~ .~~~

,

....

~

~ ~

~

"

~---

,

L~U

~V~~/lll

~~

~ ~~~

,,

~

_

. -

~

~.

~

n

~ .

~~= ~,

~

~;

g---

~

~

.

~

~

~-

~

~

~

~

~~

~

_~

~

~N ~

~ ~

~

(~seluo!suem~p) ' H ] ( ~ O )

~

~

~

~ ~

~

=

puO HO(dOD) a~omJo;Jed ;o slue!o!l;eo o

~

~~

~K

~ ~ ~

Data for absorption heat pump systems---II

3.4-

111

TCO=70~

TOE" 140~C

~ 3.0

TAe.80.C/ .c

.E ~.~ ~ ~

~

~ c ~

i

•g

I

I

o

I

I l~l

I

~

~• ~ ~

/

c.

~

I~

~

-~

~ ~ c

~

1.4

~

~

~

~ ~~

~e

-~ ~

~ /

~c

I~ ~ ~

{

~ ~.$--

~

~. .~

~

~

-

~

~ Id

--~ ~

~

~

~

Evopora~r temper~u~ Tev, (~)

Fig. 4. Plots of coe~Nen~s of ~ r f ~ a n ~

~nd flow ~fio against evaporator tem~ratu~ at ~ r ~ different abs~r~r tem~ratures. CONCLUSIONS

Possible combinations of operating temperature, the concentrations in the absorber and the generator together with their related thermodynamic design data for absorption heat pumps operating on ammonia-lithium nitrate have been presented. The interactions of these parameters for the heating mode have also been graphically illustrated. The appropriate temperature ranges are as follows: 20°C < TEv < 50°C 50°C < TAb < 100°C 50°C