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Article

Study on a Quaternary Working Pair of CaCl2-LiNO3-KNO3/H2O for an Absorption Refrigeration Cycle

by 1, 2, 1,3 and 1,3,*
1
School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China
2
State Grid Energy Conservation Service CO., Ltd., Beijing 100083, China
3
Beijing Higher Institution Engineering Research Center of Energy Conservation and Environmental Protection, University of Science and Technology Beijing, Beijing 100083, China
*
Author to whom correspondence should be addressed.
Entropy 2019, 21(6), 546; https://doi.org/10.3390/e21060546
Received: 24 April 2019 / Revised: 22 May 2019 / Accepted: 24 May 2019 / Published: 29 May 2019
(This article belongs to the Special Issue Advances in Applied Thermodynamics III)

Abstract

:
When compared with LiBr/H2O, an absorption refrigeration cycle using CaCl2/H2O as the working pair needs a lower driving heat source temperature, that is, CaCl2/H2O has a better refrigeration characteristic. However, the crystallization temperature of CaCl2/H2O solution is too high and its absorption ability is not high enough to achieve an evaporation temperature of 5 °C or lower. CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was proposed and its crystallization temperature, saturated vapor pressure, density, viscosity, specific heat capacity, specific entropy, and specific enthalpy were measured to retain the refrigeration characteristic of CaCl2/H2O and solve its problems. Under the same conditions, the generation temperature for an absorption refrigeration cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was 7.0 °C lower than that with LiBr/H2O. Moreover, the cycle’s COP and exergy efficiency with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O were approximately 0.04 and 0.06 higher than those with LiBr/H2O, respectively. The corrosion rates of carbon steel and copper for the proposed working pair were 14.31 μm∙y−1 and 2.04 μm∙y−1 at 80 °C and pH 9.7, respectively, which were low enough for engineering applications.

1. Introduction

Absorption refrigeration systems can effectively utilize not only industrial waste heat [1,2,3,4], but also low-grade renewable energy, including solar energy and geothermal energy for refrigeration [5,6,7]. As a traditional working pair, LiBr/H2O has been widely used for refrigeration [8,9,10,11,12]. However, studies on new working pairs are still ongoing, because the required temperature of driving heat source for a refrigeration cycle using LiBr/H2O even reaches 88.0 °C [13,14,15], which is too high to use for some low-grade heat sources. Lin et al. [16] studied a double-stage air-cooled NH3/H2O absorption refrigeration system and found that it could effectively lower the temperature of driving heat source for utilizing solar energy. Malinina et al. [17] analyzed the influences of temperature and humidity on a solar energy refrigeration system with LiBr/H2O and calculated the minimum heat-collecting temperatures that are based on solar energy in some cities. Mortazavi et al. [18] designed an absorption refrigeration system with a falling-film generator, which could use lower temperature waste heat or solar energy. Bourouis et al. [19] analyzed the performance of LiBr + LiNO3 + LiCl + LiI + H2O in a vertical tube and found that the crystallization temperature was 35 °C lower than LiBr solution. Sun et al. [20] studied LiBr-LiNO3 (mole ratio: 4:1)/H2O and found the alternative working pair had higher COP and less corrisivity than LiBr/H2O. Chen et al. [21] studied the performance of an absorption refrigeration system using [emim]Cu2Cl5/NH3 as working pair with the UNIFAC model, and results showed that the [emim]Cu2Cl5/NH3 system possessed several advantages, including non-crystallization and non-corrosion. Bellos et al. [22] compared the exergy efficiency between LiCl/H2O and LiBr/H2O, results showed that LiCl/H2O performed better at different ambient temperature levels. Wang et al. [23] measured the properties of different ammonia/ionic liquid working pairs. Luo et al. [24,25,26,27,28] studied various lithium nitrate-ionic liquid/water working pairs. They both found that the working pairs with ionic liquid had excellent characteristics for heating, whereas they were not suitable for refrigeration because of insufficient absorption ability. Li et al. [29,30,31,32] measured the thermophysical properties of several CaCl2-based working pairs, and found that the CaCl2-based working pairs had an excellent refrigeration characteristic. However, their strong corrosivity limited the practical applications.
In this work, to find a new working pair with excellent refrigeration characteristic for absorption refrigeration, various inorganic salts, including NaCl, KCl, LiCl, KNO3, and LiNO3, were added in CaCl2/H2O, and their crystallization temperature and saturated vapor pressure were measured. Furthermore, some other thermophysical properties and corrisivity of the proposed working pair were measured and the performance of an absorption refrigeration cycle with the proposed working pair was analyzed.

2. Experiments

2.1. Materials

Table 1 shows the purities of the reagents used in this work. Table 2 lists the detailed compositions of carbon steel and copper samples used in the corrosion experiments.

2.2. Apparatus and Methods

To analyze the performance of a working pair, its properties, such as crystallization temperature, saturated vapor pressure, density, viscosity, specific heat capacity, dissolution enthalpy, and corrosion rate, need to be measured.
The crystallization temperature was measured by a dynamic method in a precision thermostat (HX-3010, Bilang, Shanghai). The prepared solution was put in the thermostat at a slightly higher initial temperature. The crystallization temperature was measured by reducing the temperature by 1 °C every 12 hours until crystallization appeared in the solution.
The saturated vapor pressure was measured by a static method. The solution was poured into an autoclave that was assembled with a precision digital absolute pressure gauge (AX-110, Aoxin, Xi’an) and a Pt-100 thermocouple. The autoclave was placed in a precision oil bath (DKU-30, Jinghong, Shanghai) after vacuuming. The data of pressure gauge and thermocouple were obtained, respectively, after stabilization.
The density and viscosity were measured in a precision viscometer oil bath (SYP1003-H, Zhongxi, Beijing). Density measurement was carried out by a capillary pycnometer with a capillary diameter of approximately 1 mm. Ubbelohde capillary viscometers with different fine capillaries was used to carry out the viscosity measurement.
The specific heat capacity and dissolution enthalpy were measured by a micro reaction calorimeter (μRC, THT Co., UK). The measurement of specific heat capacity was conducted by making a 1 °C “step-change” in the measurement temperature. The dissolution enthalpy was measured by an isothermal method, with a solid addition accessory.
The corrosion rate of carbon steel and copper in the solution were measured by a weight loss method. The sample was immerged in the solution for 200 hours. The corrosion rate was calculated according to the mass change of the sample.
References [24,25,26,27,28] give the detailed procedures. All the above experiments were carried out at 101.3 kPa and 25 °C. The properties of water and LiBr/H2O were measured and compared with literature values to validate the above methods. In addition, three parallel experiments were carried out for each measurement to verify the reproducibility. Table 3 lists the accuracy of the instruments.

3. Results and Discussion

3.1. CaCl2/H2O

To find a working pair with excellent refrigeration characteristic, the saturated vapor pressures of CaCl2/H2O were measured and are shown in Figure 1a. Figure 1b presents the comparison of the refrigeration characteristic between LiBr/H2O and CaCl2/H2O, it shows that, for an identical pressure of 6.290 kPa, which is a typical pressure in the condenser and generator, CaCl2/H2O had a lower generation temperature than LiBr/H2O, meaning that the refrigeration characteristic of CaCl2/H2O was better than LiBr/H2O.
Figure 2 shows the absorption temperature of CaCl2/H2O under an absorption pressure of 0.872 kPa, which corresponds to the typical evaporation temperature of 5 °C. The crystallization temperature of CaCl2/H2O is also plotted in Figure 2 to illustrate the limitation from the crystallization of absorbent. The absorption temperature increased with increasing the concentration, and meet the crystallization temperature at 33.0 °C, which was the maximum absorption temperature under the given conditions. Generally, the absorption temperature in absorber for a refrigeration cycle is 37.0 °C, so the binary working pair of CaCl2/H2O could not be applied for the refrigeration cycle, because of its high crystallization temperature and insufficient absorption ability.
To improve the absorption ability and reduce the crystallization temperature of CaCl2/H2O, some salts, including NaCl, KCl, LiCl, KNO3, and LiNO3, were combined with CaCl2/H2O, and their saturated vapor pressures and crystallization temperatures were measured.

3.2. Measurement of Crystallization Temperature TC

The TC of CaCl2-NaCl/H2O, CaCl2-KCl/H2O, CaCl2-LiCl/H2O, CaCl2-KNO3/H2O, CaCl2-LiNO3/H2O, and CaCl2-LiNO3-KNO3/H2O were measured. Figure 3 gives the comparison of TC between these CaCl2-based working pairs and CaCl2/H2O. Here, the concentration is the solution’s total solute mass concentration.
Figure 3a shows CaCl2-NaCl/H2O with adding 5.0 g NaCl to CaCl2/H2O, in which CaCl2 were from 42.9 g to 61.3 g and H2O was 95.0 g. The crystallization temperatures of CaCl2-NaCl/H2O were higher than those of CaCl2/H2O under the same concentrations.
Figure 3b shows CaCl2-KCl/H2O with adding 5.0 g KCl to CaCl2/H2O, in which CaCl2 were from 78.6 g to 117.4 g and H2O was 95.0 g. The crystallization temperatures of CaCl2-KCl/H2O were approximately 20.0 °C lower than those of CaCl2/H2O under the same concentrations.
Figure 3c shows CaCl2-LiCl/H2O with adding 10.0 g LiCl to CaCl2/H2O, in which CaCl2 were from 66.7 g to 100.0 g and H2O was 90.0 g. The crystallization temperature of CaCl2-LiCl/H2O was reduced greatly when compared with that of CaCl2/H2O at 50.0 wt.%, whereas with the concentration increasing, the effect of LiCl addition on the crystallization temperature obviously decreased.
Figure 3d shows CaCl2-KNO3/H2O with adding 10.0 g KNO3 to CaCl2/H2O, in which CaCl2 were from 78.6 g to 117.4 g and H2O was 90.0 g. The crystallization temperatures of CaCl2-KNO3/H2O were lower than those of CaCl2/H2O under the same concentrations. Moreover, it decreased with increasing concentration in the range of 49.0 wt.% to 53.5 wt.%, whereas it increased with further increasing concentration.
Figure 3e shows CaCl2-LiNO3/H2O with adding 35.0 g LiNO3 to CaCl2/H2O, in which CaCl2 were from 42.9 g to 100.0 g and H2O was 65.0 g. The crystallization temperatures of CaCl2-LiNO3/H2O were significantly reduced when compared with those of CaCl2/H2O under the same concentrations. Corresponding to the concentrations ranging from 55.0 wt.% to 62.0 wt.%, which is a practical concentration range for an absorption refrigeration cycle, the crystallization temperatures of CaCl2-LiNO3/H2O were from -10.0 °C to 7.0 °C, which are sufficiently low to solve the absorbent crystallization problem in summer. However, the addition amount of 35.0 g LiNO3 was relatively large, and it is a disadvantage from the aspect of cost due to LiNO3 being much more expensive than CaCl2.
To depress the cost increase, a part of LiNO3 was replaced with KNO3 for CaCl2-LiNO3/H2O. Figure 3f shows CaCl2-LiNO3-KNO3/H2O with adding 25.0 g LiNO3 and 5.0 g KNO3 to CaCl2/H2O, in which CaCl2 were from 66.7 g to 117.4 g and H2O was 70.0 g. A reduction of crystallization temperature up to 30.0 °C was achieved from 58.0 wt.% to 65.0 wt.%, which indicated that the crystallization problem would not occur in this concentration range.

3.3. Measurement of Saturated Vapor Pressure p

p of CaCl2-LiNO3/H2O and CaCl2-LiNO3-KNO3/H2O with different mass ratios were measured and are shown in Table 4 and Table 5.
The measured p was fitted by Equation (1) [33,34,35].
log p = i = 0 4 [ A i + B i / ( T + 273.15 C i ) ] w i
where Ai, Bi, and Ci are the regression parameters. Equation (2) obtains the average absolute relative deviation (AARD) between the measured values and the fitted values.
AARD = 1 / N i = 1 N | ( P exp P f i t ) / P f i t |
where N is total number of data, Pexp is the measured or obtained value, and Pfit is the fitted value.
The regression parameters and AARD were obtained and are shown in Table 6 and Table 7, respectively.
Figure 4 and Figure 5 plot the measured p and fitted value of CaCl2-LiNO3/H2O and CaCl2-LiNO3-KNO3/H2O, respectively. The fitted value agreed well with the measured p. 60.2 wt.% for CaCl2(63.2 g)-LiNO3(35.0 g)/H2O(65.0 g) and 60.5 wt.% for CaCl2(77.3 g)-LiNO3(25.0 g)-KNO3(5.0 g)/H2O(70.0 g) were obtained, respectively, by Equation (1) at 37.0 °C and 0.872 kPa, which are the typical absorption temperature and absorption pressure for a refrigeration cycle. Meanwhile, the absorption temperatures of these two working pairs were 70.5 °C and 69.2 °C, respectively, at 6.290 kPa, which is the typical generation pressure. Therefore, CaCl2(77.3 g)-LiNO3(25.0 g)-KNO3(5.0 g)/H2O(70.0 g), with a solute mass ratio of 15.5:5:1, had been proposed as an alternative working pair for LiBr/H2O. The proposed working pair is expressed as CaCl2-LiNO3-KNO3(15.5:5:1)/H2O in this paper.
The p of this working pair was measured in order to analyze the cycle performance with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O, as shown in Table 8.
The measured p was fitted by Equation (3) and the AARD was obtained to be 1.82% by Equation (2).
log p = 1.243 8.293 / ( T + 273.15 + 3.466 × 10 3 ) + ( 1.698 × 10 1 3.894 × 10 / ( T + 273.15 + 1.944 × 10 2 ) ) × w + ( 1.503 × 10 3 + 3.797 × 10 1 / ( T + 273.15 + 2.836 × 10 2 ) ) × w 2
Figure 6 shows the measured p and fitted value. The measured p agreed well with the fitted value, which indicated that the p of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O could be obtained with the given corresponding concentration and temperature.
Figure 7 compares the refrigeration characteristic of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O and LiBr/H2O. The generation temperature of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was 74.0 °C, which was 7.0 °C lower than that of LiBr/H2O. In other words, the temperature that is required for the driving heat source could be reduced by 7.0 °C through using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O instead of LiBr/H2O.

3.4. Measurement of Density ρ

ρ of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O was measured by a capillary pycnometer method. Table 9 lists the results.
The measured ρ of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was fitted by Equation (4) and AARD was obtained to be 0.22% by Equation (2).
ρ = 1.923 × 10 2 1.139 × ( T + 273.15 ) + 1.690 × 10 3 × ( T + 273.15 ) 2 + ( 1.034 × 10 3 + 6.162 × ( T + 273.15 ) 9.146 × 10 3 × ( T + 273.15 ) 2 ) × w + ( 1.859 × 10 3 1.107 × 10 × ( T + 273.15 ) + 1.642 × 10 2 × ( T + 273.15 ) 2 ) × w 2 + ( 1.108 × 10 3 + 6.595 × ( T + 273.15 ) 9.781 × 10 3 × ( T + 273.15 ) 2 ) × w 3
Figure 8 shows the measured ρ and the fitted value. The measured ρ was highly consistent with the fitted value. The density linearly decreased with the temperature increasing, and it increased with the concentration increasing.

3.5. Measurement of Viscosity η

η of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was measured by the Ubbelohde capillary viscometer method. Table 10 shows the results.
The measured η of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was fitted by Equation (5) and the AARD was obtained to be 0.82% by Equation (2).
η = 8.099 × 10 4.721 × 10 4 / ( T + 273.15 ) + 8.480 × 10 6 / ( T + 273.15 ) 2 + ( 2.286 × 10 2 + 1.169 × 10 5 / ( T + 273.15 ) 2.278 × 10 7 / ( T + 273.15 ) 2 ) × w + ( 2.534 × 10 1.816 × 10 4 / ( T + 273.15 ) 4.422 × 10 5 / ( T + 273.15 ) 2 ) × w 2 + ( 2.224 × 10 2 + 4.127 × 10 5 / ( T + 273.15 ) + 2.716 × 10 7 / ( T + 273.15 ) 2 ) × w 3
Figure 9 shows the measured η and the fitted value. The measured η agreed well with the fitted value. η exponentially decreased with the temperature increasing, whereas it increased with the concentration increasing.

3.6. Measurement of Specific Heat Capacity Cp

Cp of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was measured with a micro reaction calorimeter. Table 11 lists the results.
The measured Cp was fitted by Equation (6) and AARD was obtained to be 0.21% by Equation (2).
C p = 2.575 + 1.951 × 10 2 × ( T + 273.15 ) 2.200 × 10 4 × ( T + 273.15 ) 2 + ( 1.121 × 10 2 6.433 × 10 4 × ( T + 273.15 ) + 7.593 × 10 6 × ( T + 273.15 ) 2 ) w + ( 3.259 × 10 4 + 5.570 × 10 6 × ( T + 273.15 ) 7.020 × 10 8 × ( T + 273.15 ) 2 ) w 2
Figure 10 shows the measured Cp and the fitted value. Cp linearly increased with increasing the temperature.

3.7. Calculation of Specific Enthalpy h

3.7.1. Cp of CaCl2, LiNO3, KNO3 and H2O

The Cp of solid KNO3 was measured and is shown in Table 12, Cp of CaCl2, LiNO3, and H2O are given in Reference Literature [29].

3.7.2. Measurement of Dissolution Enthalpy ΔHmix

ΔHmix of KNO3, LiNO3, and CaCl2 with a mass ratio of 15.5:5:1 were measured at 25.0 °C and are shown in Table 13.

3.7.3. Calculation of Specific Enthalpy h

h of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O can be obtained from the measured Cp and ΔHmix [25,36,37]. Table 14 lists the obtained results.
The obtained h was fitted by Equation (7) and AARD was obtained to be 0.07% by Equation (2).
h = 3.151 × 10 2 1.193 × w + 6.998 × 10 3 × w 2 + ( 2.971 2.553 × 10 3 × w 1.817 × 10 4 × w 2 ) ( T + 273.15 ) + ( 1.775 × 10 3 + 1.198 × 10 4 × w 1.304 × 10 6 × w 2 ) ( T + 273.15 ) 2
Figure 11 shows the obtained h and the fitted value. h linearly increased with increasing the temperature, and the slope of line slightly increased with reducing the concentration.

3.8. Calculation of Specific Entropy s

s of a solution can be also obtained from the measured Cp and ΔHmix [38]. s of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O was obtained and is shown in Table 15.
The obtained s of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O was fitted by Equation (8) and the AARD was obtained to be 0.84% by Equation (2).
s = 2.662 × 10 + 1.370 × 10 2 × w 2.828 × 10 2 × w 2 + 1.967 × 10 2 × w 3 + ( 2.333 × 10 1 + 1.315 × w + 2.735 × w 2 1.892 × w 3 ) ( T + 273.15 ) + ( 6.999 × 10 4 + 4.199 × 10 3 × w 8.788 × 10 3 × w 2 + 6.062 × 10 3 × w 3 ) ( T + 273.15 ) 2 + ( 7.282 × 10 7 4.461 × 10 6 × w + 9.373 × 10 6 × w 2 6.469 × 10 6 × w 3 ) ( T + 273.15 ) 3
Figure 12 shows the obtained s and the fitted value. s increased with the temperature increasing and decreased with the concentration increasing when the temperature was above 28 °C, whereas it changed little with the concentration when the temperature was below 28 °C.

3.9. Application for an Absorption Refrigeration Cycle

3.9.1. Absorption Refrigeration Cycle Using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O

Figure 13a shows the schematic of an absorption refrigeration cycle. Figure 13b is the P-T diagram of the cycle, and the points that are marked in the two diagrams are one-to-one correspondence.
The working conditions are given, as follows: the evaporation temperature was 5.0 °C; the absorption temperature and condensation temperature were 37.0 °C; and, the evaporation and condensation pressures were 0.872 kPa and 6.290 kPa, respectively. The concentration of dilute solution for CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was figured out to be 60.5 wt.% by Equation (3), and the strong solution was 63.5 wt.%, with a concentration difference of 3.0 wt.%, thus, the generation temperature of the cycle was determined to be 74.0 °C by Equation (3). The same method was applied to calculate the generation temperature while using LiBr/H2O and other CaCl2-based working pairs, including CaCl2-LiBr-LiNO3-KNO3(16.2:2:2:1)/H2O, CaCl2-LiNO3-LiBr(8.72:1:1)/H2O, and CaCl2-LiBr(1.35:1)/H2O. Table 16 lists the results.
As seen in Table 16, the generation temperature was reduced by 7.0 °C through the use of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O instead of LiBr/H2O. The generation temperature differences between the four CaCl2-based working pairs were relatively small.

3.9.2. Analysis of COP and Exergy Efficiency

To analyze the performance of a refrigeration cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O, the state parameters of typical points in Figure 13 were obtained by Equations (3), (7) and (8). Table 17 lists the results.
The coefficient of performance (COP) for the absorption refrigeration cycle can be defined as:
COP = Q E Q G = h 1 h 3 h 4 h 4 + α ( h 4 h 7 )
where α represents circulating ratio.
COP was obtained to be 0.801 when using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O as the working pair. The COPs for other working pairs were obtained with the same method, and the results are listed in Table 18.
Table 18 shows that, through using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O instead of LiBr/H2O, the COP was improved by 0.04. Moreover, the exergy destruction in each part of the cycle were analyzed to further compare the performance between CaCl2-LiNO3-KNO3(15.5:5:1)/H2O and LiBr/H2O. Exergy is defined as the maximum possible reversible work that can be obtained from a stream:
E = ( h h 0 ) ( T 0 + 273.15 ) ( s s 0 )
where T0 represents the environment temperature that was taken as 25 °C in this paper.
The exergy destructions for each part of the absorption refrigeration cycle were obtained as follows [39].
Evaporator:
Δ E E = D 3 E 3 D 1 E 1 + Q E ( T 0 T E 1 )
Condenser:
Δ E C = D 4 E 4 D 3 E 3 Q C ( 1 T 0 T C )
Absorber:
Δ E A = D 8 E 8 + D 1 E 1 D 2 E 2 Q A ( 1 T 0 T A )
Generator:
Δ E G = D 7 E 7 D 4 E 4 D 4 E 4 + Q G ( 1 T 0 T G )
Heat exchanger:
Δ E H E X = D 2 E 2 + D 4 E 4 D 7 E 7 D 8 E 8
Table 19 compares the exergy destructions of the absorption cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O and LiBr/H2O. Except the exergy destruction of the evaporator was equal because of the same evaporation condition, the exergy destructions of other parts for CaCl2-LiNO3-KNO3(15.5:5:1)/H2O were lower than those for LiBr/H2O. For the absorption refrigeration cycle, the exergy efficiency (ηE) can be defined as:
η E = Q E ( T E / T 0 1 ) Q G ( 1 T Q / T 0 )
The ηE of the absorption refrigeration cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O and LiBr/H2O were obtained to be 0.327 and 0.272, respectively. When compared with COP, the difference in exergy efficiency between the two working pairs was more distinct, which further showed the advantage of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O as an alternative working pair.
Figure 14 and Figure 15 show the changes of generation temperature and efficiencies (COP and ηE) for CaCl2-LiNO3-KNO3(15.5:5:1)/H2O, with the evaporation temperature varying from 5 °C to 15 °C. As shown in Figure 14a, the generation temperature decreased almost linearly with increasing the evaporation temperature. As shown in Figure 14b, the COP of the absorption refrigeration cycle increased with the evaporation temperature increasing, whereas the exergy efficiency decreased with the evaporation temperature increasing.
Figure 15 shows the variations of COP and ηE with the solution heat exchanger efficiency. COP and ηE increased almost linearly with the heat exchanger efficiency increasing, and the increasing slope of COP was greater than that of ηE.

3.10. Measurement of Corrosion Rate RC

Generally, carbon steel is used as the structural material and copper is used as the heat exchange material for absorption heat pump. The RC of carbon steel and copper in 63.5 wt.% solution of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O were measured at 80.0 °C and pH 9.7. Figure 16 gives the comparison of RC in 63.5 wt.% solution of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O, 59.4 wt.% solution of LiBr/H2O, and 60.3 wt.% solution of CaCl2-LiNO3-LiBr(8.72:1:1)/H2O.
Figure 16 shows that the Rc of carbon steel in 63.5 wt.% solution of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was 14.31 μm∙y−1. Although the corrosivity of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O to carbon steel was stronger than that of LiBr/H2O, it was still acceptable for practical applications. On the other hand, the corrosivity of CaCl2-LiNO3-LiBr(8.72:1:1)/H2O to carbon steel was too strong to be applied, even though it had the lowest generation temperature among the CaCl2-based working pairs. The Rc of copper in 63.5 wt.% solution of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O was 2.04 μm∙y−1, which was smaller than that in 59.4 wt.% solution of LiBr/H2O and it could meet the requirements for engineering applications.

4. Conclusions

  • When compared with LiBr/H2O, for an identical adsorption temperature at 0.872 kPa, which is a typical pressure of absorber, CaCl2/H2O had a lower absorption temperature at 6.290 kPa, which is a typical pressure of generator, meaning that CaCl2/H2O basically had a better refrigeration characteristic for an absorption refrigeration cycle. However, the absorption ability of CaCl2/H2O was not strong enough for achieving an evaporation temperature of 5 °C or lower, because of its high crystallization temperature.
  • The crystallization temperature was significantly lowered when combining CaCl2/H2O with LiNO3 or LiNO3+KNO3. As a result, the absorption ability of CaCl2-LiNO3/H2O or CaCl2-LiNO3-KNO3/H2O was essentially improved.
  • For an absorption refrigeration cycle using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O as the working pair, the generation temperature that is required for achieving an evaporation temperature of 5 °C was 74.0 °C, which was 7.0 °C lower than that using LiBr/H2O.
  • When compared with LiBr/H2O under the same conditions, COP and ηE of the absorption refrigeration cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O were improved by 0.04 and 0.06, respectively.
  • RC of carbon steel and copper in 63.5 wt.% solution of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O at 80.0 °C and pH 9.7 were 14.31 and 2.04 μm∙y−1, respectively, which indicated that the corrosivity of the proposed working pair could meet the requirements for practical applications.

Author Contributions

Writing—Original Draft preparation, Y.L.; data curation, N.L.; methodology, C.L.; Writing—Review and Editing, Q.S.

Funding

This work was supported by The National Key Research and Development Program of China (2016YFC0400408).

Conflicts of Interest

The authors declare no conflict of interest.

Nomenclature

Ttemperature, °C
wmass concentration, %
TCcrystallization temperature, °C
psaturated vapor pressure, kPa
ρdensity, g·cm−3
ηdynamic viscosity, mPa·s
Cpspecific heat capacity, kJ·kg−1·K−1
ΔHmixdissolution enthalpy, kJ·kg−1
hspecific enthalpy, kJ·kg−1
sspecific entropy, kJ·kg−1·K−1
AARDaverage absolute relative deviation
acirculation ratio
COPcoefficient of performance
Eexergy
ΔEexergy destrction
ηEexergy efficiency
RCcorrosion rate, μm∙y−1

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Figure 1. (a) Saturated vapor pressure of CaCl2/H2O; (b) Comparison of the refrigeration characteristic between LiBr/H2O and CaCl2/H2O.
Figure 1. (a) Saturated vapor pressure of CaCl2/H2O; (b) Comparison of the refrigeration characteristic between LiBr/H2O and CaCl2/H2O.
Entropy 21 00546 g001
Figure 2. Crystallization temperature and absorption temperature for CaCl2/H2O.
Figure 2. Crystallization temperature and absorption temperature for CaCl2/H2O.
Entropy 21 00546 g002
Figure 3. Comparison of TC between CaCl2/H2O and other CaCl2-based working pairs: (a) CaCl2-NaCl/H2O; (b) CaCl2-KCl/H2O; (c) CaCl2-LiCl/H2O; (d) CaCl2-KNO3/H2O; (e) CaCl2-LiNO3/H2O; and, (f) CaCl2-LiNO3-KNO3/H2O.
Figure 3. Comparison of TC between CaCl2/H2O and other CaCl2-based working pairs: (a) CaCl2-NaCl/H2O; (b) CaCl2-KCl/H2O; (c) CaCl2-LiCl/H2O; (d) CaCl2-KNO3/H2O; (e) CaCl2-LiNO3/H2O; and, (f) CaCl2-LiNO3-KNO3/H2O.
Entropy 21 00546 g003
Figure 4. p of CaCl2-LiNO3/H2O with different mass ratio.
Figure 4. p of CaCl2-LiNO3/H2O with different mass ratio.
Entropy 21 00546 g004
Figure 5. p of CaCl2-LiNO3-KNO3/H2O with different mass ratio.
Figure 5. p of CaCl2-LiNO3-KNO3/H2O with different mass ratio.
Entropy 21 00546 g005
Figure 6. p of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Figure 6. p of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Entropy 21 00546 g006
Figure 7. Comparison of the refrigeration characteristic between LiBr/H2O and CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Figure 7. Comparison of the refrigeration characteristic between LiBr/H2O and CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Entropy 21 00546 g007
Figure 8. ρ of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Figure 8. ρ of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Entropy 21 00546 g008
Figure 9. η of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Figure 9. η of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Entropy 21 00546 g009
Figure 10. Cp of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O.
Figure 10. Cp of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O.
Entropy 21 00546 g010
Figure 11. h of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O.
Figure 11. h of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O.
Entropy 21 00546 g011
Figure 12. s of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Figure 12. s of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Entropy 21 00546 g012
Figure 13. (a) Schematic of the absorption refrigeration cycle; (b) P-T diagram of the absorption refrigeration cycle.
Figure 13. (a) Schematic of the absorption refrigeration cycle; (b) P-T diagram of the absorption refrigeration cycle.
Entropy 21 00546 g013
Figure 14. (a) Variation of the generation temperature with the evaporation temperature; and, (b) Variations of COP and ηE with the evaporation temperature.
Figure 14. (a) Variation of the generation temperature with the evaporation temperature; and, (b) Variations of COP and ηE with the evaporation temperature.
Entropy 21 00546 g014
Figure 15. Variations of COP and ηE with the heat exchanger efficiency.
Figure 15. Variations of COP and ηE with the heat exchanger efficiency.
Entropy 21 00546 g015
Figure 16. RC of carbon steel and copper for CaCl2-LiNO3-KNO3(15.5:5:1)/H2O, CaCl2-LiNO3-LiBr(8.72:1:1)/H2O and LiBr/H2O.
Figure 16. RC of carbon steel and copper for CaCl2-LiNO3-KNO3(15.5:5:1)/H2O, CaCl2-LiNO3-LiBr(8.72:1:1)/H2O and LiBr/H2O.
Entropy 21 00546 g016
Table 1. Purity of the used regents.
Table 1. Purity of the used regents.
ReagentMass Concentration PurityProvenance
CaCl2>0.96Sinopharm Chemical Reagent Beijing
NaCl>0.995Sinopharm Chemical Reagent Beijing
KNO3>0.99Sinopharm Chemical Reagent Beijing
KCl>0.995Sinopharm Chemical Reagent Beijing
LiCl>0.95Tianjin Jinke Chemical
LiNO3>0.995Tianjin Jinke Chemical
Ultrapure water Home-made
Table 2. Chemical compositions of carbon steel and copper.
Table 2. Chemical compositions of carbon steel and copper.
ComponentCMnSiPSZnPbSnFeCu
Carbon steel Q2350.160.530.30.0350.04------balance--
Copper T6----0.006--0.010.0050.050.050.05balance
Table 3. Measuring range and accuracy of main instruments.
Table 3. Measuring range and accuracy of main instruments.
InstrumentParameterAccuracy
Analytical balance0–2100 g±0.1 g
Precision thermostat−30–150 °C±0.5 °C
Oil bath20–300 °C±1.0 °C
Digital absolute pressure gauge0–110 kPa±0.01 kPa
Precision viscometer oil bath0–230 °C±0.05 °C
Capillary pycnometer50 mL±0.03%
Ubbelohde capillary viscometer0.36 mm, 0.46 mm,
0.58 mm, 073 mm
±0.02%
Micro reaction calorimeter0–180 °C±0.001 °C
Table 4. p of CaCl2-LiNO3/H2O with different mass ratio.
Table 4. p of CaCl2-LiNO3/H2O with different mass ratio.
x/g Saturated Vapor Pressure p (kPa) at Each Temperature T (°C)
CaCl2(x)-LiNO3(35.0 g)/H2O(65.0 g)
42.9T20.025.030.535.040.045.350.455.760.2
p0.4570.6410.9341.2561.6932.3693.2784.4315.707
T65.370.875.080.085.090.095.0100.0
p7.3769.63211.82515.20419.00223.33128.10134.022
47.1T20.025.030.235.040.145.350.255.559.9
p0.4190.5850.8341.1381.5352.1392.9483.9985.136
T65.270.375.180.285.290.095.4100.3
p6.8238.73911.03514.11817.69221.77026.70132.375
51.5T20.025.029.935.040.145.250.055.259.6
p0.3720.5200.7331.0101.3771.9102.6173.5644.565
T65.169.875.280.485.390.095.8100.6
p6.2697.84610.24413.03116.38220.20825.30030.728
56.3T20.025.030.335.340.145.150.055.760.1
p0.3300.4600.6740.9211.2331.6882.3363.2174.188
T65.370.575.079.985.090.495.0101.0
p5.5237.3339.22811.68814.99818.86922.50027.967
61.3T20.125.030.335.240.245.150.155.360.0
p0.2950.4190.6030.8261.1241.5312.1132.8443.704
T65.070.275.180.185.190.595.1100.5
p4.8946.4908.34910.67113.67817.23320.68525.265
66.7T20.225.030.335.140.245.150.154.959.9
0.2690.3780.5520.7521.0241.3751.8602.4713.220
T64.669.875.280.285.290.595.2100.0
4.2655.6477.4709.65412.35815.59718.87022.562
72.4T20.125.030.135.040.044.950.055.260.4
p0.2470.3410.4920.6710.8991.1861.6572.2373.092
T64.670.075.080.485.190.095.5100.2
p3.9305.2686.6788.67810.96013.50717.12720.709
78.6T20.125.030.035.140.045.150.155.059.9
p0.2180.2980.4300.5920.8041.1061.5152.0192.722
T65.270.274.980.285.190.095.5100.3
p3.7094.8106.0997.8059.90112.20615.70919.204
85.2T30.135.041.145.051.154.960.064.969.9
p0.3900.5290.7680.9811.4201.7802.3853.2054.185
T75.080.285.390.295.4100.6
p5.6247.1359.09810.99613.75617.535
92.3T45.150.154.960.865.470.275.581.185.1
p0.8861.1881.6452.3033.0483.9035.2266.7778.311
T90.595.8100.0
p10.27612.82015.447
100.0T65.770.476.780.285.190.295.2100.1
p2.7113.5525.0506.0007.4329.26011.38313.858
Table 5. p of CaCl2-LiNO3-KNO3/H2O with different mass ratio.
Table 5. p of CaCl2-LiNO3-KNO3/H2O with different mass ratio.
y/g Saturated Vapor Pressure p (kPa) at Each Temperature T (°C)
CaCl2(y)-LiNO3(25.0 g)-KNO3(5.0 g)/H2O(70.0 g)
66.7T20.025.030.135.540.045.350.054.960.0
p0.3520.5110.7411.0641.4341.9872.6383.5084.660
T65.170.175.280.087.289.995.0100.0
p6.1198.02410.49013.00117.34619.22323.45028.590
72.4T20.025.030.234.940.645.650.055.260.4
p0.3150.4550.6500.9111.3531.8502.4033.2504.283
T65.169.975.280.385.089.794.9100.0
p5.5607.1069.46911.91114.32717.20021.02126.025
78.6T20.025.029.935.140.045.050.054.960.0
p0.2590.3710.5300.7621.0491.4271.9402.6343.552
T65.169.875.580.185.089.994.9100.1
p4.8256.3068.54610.55512.91315.54018.89823.535
85.2T20.025.030.035.040.545.050.055.060.2
p0.2190.3120.4450.6270.9281.2391.7402.3113.200
T65.069.875.180.085.190.095.2100.2
p4.2055.4997.4029.37811.78917.90921.505
92.3T20.025.030.035.439.945.050.055.160.1
p0.1980.2850.3990.5810.7931.1361.5632.1502.925
T65.270.075.379.985.290.095.5100.2
p3.8755.0486.6838.44810.85913.42916.90619.867
100.0T41.044.950.055.060.265.070.175.180.3
p0.6730.8891.2441.7302.4543.3494.5195.9117.656
T85.289.994.999.9
p9.76112.06014.96018.163
108.3T60.065.270.075.280.184.890.495.1100.1
p2.2053.0454.0515.2526.6868.46410.99313.11015.587
117.4T82.085.190.095.0100.3
p5.9216.9719.00911.30314.387
Table 6. Regression parameters for CaCl2-LiNO3/H2O and average absolute relative deviation (AARD) value.
Table 6. Regression parameters for CaCl2-LiNO3/H2O and average absolute relative deviation (AARD) value.
iAiBiCiAARD
04.896 × 10−1−1.985 × 100−3.624 × 1001.55%
1−1.172 × 10−15.756 × 10−1−1.189 × 101
21.024 × 10−2−2.990 × 10−1−3.963 × 101
3−1.768 × 10−43.046 × 10−3−1.894 × 101
49.452 × 10−7−8.957 × 10−6−4.335 × 100
Table 7. Regression parameters for CaCl2-LiNO3-KNO3/H2O and AARD value.
Table 7. Regression parameters for CaCl2-LiNO3-KNO3/H2O and AARD value.
iAiBiCiAARD
0−2.262 × 10−2−3.844 × 10−15.668 × 10−12.34%
15.616 × 10−11.184 × 1001.367 × 100
2−2.523 × 10−2−1.498 × 10−25.033 × 100
34.274 × 10−4−3.524 × 10−3−3.042 × 101
4−2.421 × 10−62.944 × 10−5−1.620 × 101
Table 8. p of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 8. p of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
w/wt.% Saturated Vapor Pressure p (kPa) at Each Temperature T (°C)
50.0T20.125.730.235.340.645.050.755.460.0
p0.6340.9011.2251.7052.3713.0644.3255.6267.206
T65.270.775.080.985.790.095.2100.0
p9.33612.07514.80019.10023.53627.93133.51940.578
55.0T21.228.032.135.039.945.152.055.660.0
p0.4430.7120.9391.1481.5692.2103.4074.2495.387
T65.270.275.080.985.090.495.0100.0
p7.0609.01611.30114.82517.69921.91226.01131.898
60.0T21.026.130.035.041.045.050.055.160.4
p0.2800.4120.5410.7691.1661.4922.0712.8554.026
T65.570.275.080.085.490.495.2100.1
p5.3556.9018.87311.10614.06317.26821.17625.912
65.0T25.130.035.040.545.050.055.660.565.6
p0.2260.3410.4900.7440.9851.3391.9582.6753.665
T71.175.480.185.290.094.6100.5
p4.9716.2827.7499.89412.39515.24119.243
Table 9. ρ of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 9. ρ of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
w/wt.%Density ρ (g·cm−3) at Each Temperature T (°C)
50.0T20.030.040.050.060.070.080.090.0100.0
ρ1.46141.45631.44881.44121.43521.42781.42151.41411.4067
55.0T20.030.040.050.060.070.080.090.0100.0
ρ1.51811.51111.50421.49771.49061.48341.47611.46961.4618
60.0T20.030.040.050.060.070.080.090.0100.0
ρ1.57841.57131.56421.55471.54951.54201.53511.52871.5229
65.0T 40.050.060.070.080.090.0100.0
ρ 1.62451.61851.61311.60581.59911.59151.5820
Table 10. η of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 10. η of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
w/wt.%Viscosity η (mPa·s) at Each Temperature T (°C)
50.0T20.030.040.050.060.070.080.090.0100.0
H20.1314.5110.568.005.984.774..113.472.95
55.0T20.030.040.050.060.070.080.090.0100.0
H45.5129.5721.6315.4011.427.796.195.184.35
60.0T20.030.040.050.060.070.080.090.0100.0
H144.0581.8851.6633.4824.0716.9112.519.477.71
65.0T 40.050.060.070.080.090.0100.0
H 144.9080.9752.2637.0725.9119.3814.55
Table 11. Cp of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 11. Cp of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
w/wt.% Specific Heat Capacity Cp (kJ·kg−1·K −1) at Each Temperature T (°C)
50.0T10.020.030.040.050.060.070.080.090.0100.0
Cp2.4382.4442.4582.4732.4872.5012.5182.5272.5422.563
55.0T10.020.030.040.050.060.070.080.090.0100.0
Cp2.3132.3212.3352.3502.3662.3802.4002.4172.4322.452
60.0T10.020.030.040.050.060.070.080.090.0100.0
Cp2.1892.1932.2062.2162.2272.2412.2542.2662.2862.303
65.0T10.020.030.040.050.060.070.080.090.0100.0
Cp2.0392.0452.0572.0712.0852.0982.1102.1272.1302.146
Table 12. Cp of solid KNO3 at atmosphere pressure.
Table 12. Cp of solid KNO3 at atmosphere pressure.
Reagent Specific Heat Capacity Cp (kJ·kg−1·K−1) at Each Temperature T (°C)
KNO3T10.020.030.040.050.060.070.080.090.0100.0
Cp0.9300.9520.9680.9740.9881.0401.0531.0721.0901.119
Table 13. ΔHmix of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O at 25.0 °C.
Table 13. ΔHmix of CaCl2-LiNO3-KNO3(15.5:5:1) /H2O at 25.0 °C.
w/wt.%50.055.060.065.0
ΔHmix/kJ·kg−1149.310150.501150.275151.292
Table 14. h of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 14. h of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
w/wt.% Specific Enthalpy h (kJ·kg−1) at Each Temperature T (°C)
50.0T10.020.030.040.050.060.070.080.090.0100.0
h296.787321.185345.720370.395395.214420.183445.305470.584496.025521.632
55.0T10.020.030.040.050.060.070.080.090.0100.0
h293.028316.239339.568363.026386.622410.368434.272458.345482.598507.039
60.0T10.020.030.040.050.060.070.080.090.0100.0
h290.874312.767334.776356.907379.172401.578424.134446.849469.733492.793
65.0T10.020.030.040.050.060.070.080.090.0100.0
h287.666308.113328.685349.382370.205391.155412.233433.438454.773476.237
Table 15. s of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 15. s of CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
w/wt.% Entropy s (kJ·kg−1·K−1) at Each Temperature T (°C)
50.0T10.020.030.040.050.060.070.080.090.0100.0
s1.4121.4961.5781.6581.7361.8131.8891.9632.0362.108
55.0T10.020.030.040.050.060.070.080.090.0100.0
s1.4171.4981.5761.6521.7271.8001.8721.9432.0142.083
60.0T10.020.030.040.050.060.070.080.090.0100.0
s1.4221.5001.5741.6451.7161.7851.8521.9191.9852.050
65.0T10.020.030.040.050.060.070.080.090.0100.0
s1.4311.5021.5711.6381.7041.7691.8321.8951.9552.016
Table 16. Concentration and generation temperature for different working pairs.
Table 16. Concentration and generation temperature for different working pairs.
Working PairCaCl2-LiNO3-
KNO3
(15.5:5:1)/H2O
LiBr/
H2O
CaCl2-LiBr-LiNO3-
KNO3(16.2:2:2:1)
/H2O
CaCl2-LiNO3-
LiBr
(8.72:1:1)/H2O
CaCl2-LiBr
(1.35:1)
/H2O
Dilute solution/wt.%60.556.458.557.355.8
Strong solution/wt.%63.559.461.560.358.8
Generation temperature/°C74.081.074.873.374.8
Table 17. State parameters of streams in the cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
Table 17. State parameters of streams in the cycle with CaCl2-LiNO3-KNO3(15.5:5:1)/H2O.
PointStreamp/kPaT/°Cw/wt.%h/kJ·kg−1D/kg·s−1s/kJ·kg−1·K−1
1Water0.8725.00439.61.00.07621
Vapor0.8725.002927.91.09.02690
2Dilute solution0.87237.060.5349.221.20.09149
3Water6.29037.00573.51.00.53190
4Strong solution6.29074.063.5424.420.20.33201
Vapor6.29074.003054.21.08.5368
5Dilute solution6.29069.260.5420.921.20.31351
6Strong solution0.87241.063.5353.720.20.11525
7Dilute solution--63.960.5409.921.20.27782
8Strong solution--44.363.5360.720.20.13754
Table 18. Coefficient of performance (COP) of the cycle with different working pairs.
Table 18. Coefficient of performance (COP) of the cycle with different working pairs.
Working PairCaCl2-LiNO3-KNO3
(15.5:5:1)
/H2O
LiBr
/H2O
CaCl2-LiBr-LiNO3-KNO3
(16.2:2:2:1)
/H2O
CaCl2-LiNO3-LiBr
(8.72:1:1)
/H2O
CaCl2-LiBr
(1.35:1)
/H2O
COP0.8010.7620.7930.8050.788
Table 19. The exergy destruction in each part of absorption refrigeration cycle using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O and LiBr/H2O.
Table 19. The exergy destruction in each part of absorption refrigeration cycle using CaCl2-LiNO3-KNO3(15.5:5:1)/H2O and LiBr/H2O.
PartExergy Destruction/kW
CaCl2-LiNO3-KNO3
(15.5:5:1)/H2O
LiBr/H2O
Evaporator0.50.5
Condenser0.40.8
Absorber52.155.3
Generator282.6332.7
Heat exchanger25.531.4

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Li, Y.; Li, N.; Luo, C.; Su, Q. Study on a Quaternary Working Pair of CaCl2-LiNO3-KNO3/H2O for an Absorption Refrigeration Cycle. Entropy 2019, 21, 546. https://doi.org/10.3390/e21060546

AMA Style

Li Y, Li N, Luo C, Su Q. Study on a Quaternary Working Pair of CaCl2-LiNO3-KNO3/H2O for an Absorption Refrigeration Cycle. Entropy. 2019; 21(6):546. https://doi.org/10.3390/e21060546

Chicago/Turabian Style

Li, Yiqun, Na Li, Chunhuan Luo, and Qingquan Su. 2019. "Study on a Quaternary Working Pair of CaCl2-LiNO3-KNO3/H2O for an Absorption Refrigeration Cycle" Entropy 21, no. 6: 546. https://doi.org/10.3390/e21060546

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