- Email: [email protected]
Sodium Thiocyanate absorption system” by Linghui Zhu and Junjie Gu, Renewable Energy, 35 (2010), 1940–1946
Renewable Energy 147 (2020) 2522e2524
Contents lists available at ScienceDirect
Renewable Energy journal homepage: www.elsevier.com/locate/renene
Thermodynamic discussion on “Second law-based thermodynamic analysis of Ammonia/Sodium Thiocyanate absorption system” by Linghui Zhu and Junjie Gu, Renewable Energy, 35 (2010), 1940e1946 Dheerendra Vikram Singh*, Tikendra Nath Verma National Institute of Technology- Manipur, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A paper has been published in Renewable Energy, second law-based thermodynamic analysis of Ammonia/Sodium Thiocynate vapour absorption refrigeration (VAR) system. Linghui Zhu and Junjie Gu have done exergy analysis and estimated exergy loss rate using second law analysis under different headings. The present paper attempts to discuss and comments on the calculation procedure, calculated results and mathematical expressions of the past published work of Linghui Zhu and Junjie Gu. Authors have also presented correction against each comment which must be used by future researchers. This study is the appropriate corrigendum for the past published work of Linghui Zhu and Junjie Gu. © 2019 Published by Elsevier Ltd.
Keywords: VAR Ammonia/Sodium Thiocynate Exergy analysis
1. Introduction
2. Discussion 1
A paper had been published on Renewable Energy, second lawbased thermodynamic analysis of Ammonia/Sodium Thiocynate absorption system by Linghui Zhu and Junjie Gu in 2010. They [1] have performed exergy analysis under the second law on Ammonia/Sodium Thiocynate operated VAR system. Authors have presented schematic diagram of VAR system which have been used by Linghui Zhu et al. in their analysis. Linghui Zhu et al. [1] have presented procedure of calculation of the thermodynamic properties which have numerous mathematical equations and consists the essential part of their past published work. Linghui Zhu and Junjie Gu have formulated mathematical expressions from fundamental exergy balance equation for estimating exergy loss rate in major components of VAR system and also presented estimated results. Variations in COP (coefficient of performance) & ECOP (exergetic coefficient of performance) are also depicted with variations in temperature of different components. Authors have found the essential reasons for discussing specific sections of past published work [1] and authors have also proposed the corrections on the discussions. Fig. 1 illustrates the system description which used in past work [1].
Linghui Zhu et al. [1] have presented mathematical expression for predicting the specific heat of superheated ammonia vapour to be used for calculating thermodynamic properties of working fluid. The mathematical expression (23) [1] for this specific heat of superheated ammonia vapour is presented below:
Cp ¼
https://doi.org/10.1016/j.renene.2019.11.041 0960-1481/© 2019 Published by Elsevier Ltd.
di ðT 273:15Þi
(1)
i¼0
This Equation (1) consists of the value of coefficient di and its value is wrongly reported in the published work [1]. Proposed correction: it is typographical mistake and its correct value is 1.7767 instead of 1.7467.
3. Discussion 2 In subsection 2.2 [1], mathematical expressions for estimating exergy loss rate in major components of VAR system have formulated under equation (26) to (30) [1] which have presented below: :
DOI of original article: https://doi.org/10.1016/j.renene.2019.09.097. * Corresponding author. E-mail address: [email protected] (D.V. Singh).
6 X
:
:
:
:
DЕG ¼ m8 E8 m7 E7 m1 E1 þ QG 1
T0 TG
(2)
D.V. Singh, T.N. Verma / Renewable Energy 147 (2020) 2522e2524
2523
exergy of output stream flow in component is taken as negative [2e7]. This work [1] have also obeyed this rule and deduced the mathematical expression for estimating the exergy loss rate in condenser, evaporator, absorber and HEX (Generator absorber heat exchanger) but exergy rate in generator is wrongly formulated. From Fig. 1, stream 7 is entering in generator and stream 1 & 8 are leaving the generator. Therefore correct mathematical expression of exergy loss rate in generator is presented in equation (7). :
:
:
:
:
DЕG ¼ m7 E7 m8 E8 m1 E1 þ QG 1
T0 TG
(7)
4. Discussion 3 Linghui Zhu et al. [1] have presented the values of the specific exergy at each salient point of VAR cycle in their published work [1]. Present work found the discussion opportunity to correct the values of specific exergy at thermodynamic states 1, 2, 8, 9 & 10. Proposed Correction: Fundamental equation of specific exergy is presented in equation (8).
Fig. 1. The schematic of a single stage VAR cycle [1].
:
DЕ
:
: А ¼ m4 E4 þ m10
:
:
:
:
DЕ C ¼ m1 E1 m2 E2 QC 1 :
:
:
:
DЕE ¼ m3 E3 m4 E4 þ QE 1 :
e ¼ ðh h0 Þ T0 ðs s0 Þ
T E10 m5 E5 QA 1 0 TA :
:
:
T0 TC
T0 TE
In this work, for this discussion, the correct values of specific exergy is estimated at each salient thermodynamic state of VAR system and reported in Table 1. The term h and s are specific enthalpy and entropy of fluid at temperature of state while h0 and s0 are the specific enthalpy and specific entropy at dead state and as h0 ¼ 315.88 kJ/kg & s0 ¼ 1.123 kJ/kg-k [1]. Remarkable difference can be observed in the value of specific exergy at the thermodynamic states 1, 2, 8, 9 & 10 from Table 1 very easily.
(3)
(4)
(5)
:
DЕ GAX ¼ m6 ðE6 E7 Þ þ m8 ðE8 E9 Þ
(8)
5. Discussion 4
(6)
Values of exergy destruction in generator & absorber and values of non dimensional exergy loss (%) in major components of VAR system are reported incorrect in Table 2 & Table 3 [1] using incorrect values of specific exergy [1].
In those above following equations, exergy rate in generator is not formulated correctly. Proposed correction: According to formulation principle, exergy of input stream flow in component is taken as positive and Table 1 Values of specific exergy taken from present work and past published work [1]. State
T (0C)
x (%)
:
m (kg/s)
h (kJ/kg)
s (kJ/kg-k)
h0 (kJ/kg)
s0 (kJ/kg-k)
t0 (k)
P (kPa)
e (kJ/kg)
[1] 1 2 3 4 5 6 7 8 9 10
e (kJ/kg) Present Study
90 25 25 10 25 25 67.92 90 38 38
100 100 100 100 0.4618 0.4618 0.4618 0.3843 0.3843 0.3843
0.0038 0.0038 0.0038 0.0038 0.03 0.03 0.03 0.0262 0.0262 0.0262
1689.7 315.88 315.88 1449.5 101.847 101.847 15.767 71.783 62.767 62.767
4.337 1.123 1.123 5.473 0.726 0.726 1.033 1.056 0.747 0.747
315.88 315.88 315.88 315.88 101.847 101.847 101.847 101.847 101.847 101.847
1.123 1.123 1.123 1.123 0.726 0.726 0.726 0.726 0.726 0.726
298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15
1002.6 1002.6 290.76 290.76 290.76 1002.6 1002.6 1002.6 1002.6 290.76
411.979 0 0 ¡166.979 0 0 26.08 52.072 9.62 9.62
415.57 0 0 ¡163.33 0 0 26.082 75.241 32.819 32.819
Table 2 Comparative analysis of exergy & non dimensional exergy loss from present study & past published work [1]. Components
Exergy loss rate (kW) [1]
Exergy loss rate from this study(kW)
Non dimensional exergy loss (%) [1]
Non dimensional exergy loss (%) from this study
Generator Condenser Evaporator Absorber HEX Total
0.4107 1.5655 0.0651 0.3825 0.3299 1.9887
0.411252a 1.5655 0.0648 - 0.38248 0.329842 1.9889
14.91 56.85 2.37 13.89 11.98 100
20.67721 78.7113 3.258059 19.2306 16.58403 100
a This value is also incorrect because it is calculated using wrong mathematical expression which has been presented by Linghui Zhu et al. [1] and its proposed correction has been already given under discussion 2.
2524
D.V. Singh, T.N. Verma / Renewable Energy 147 (2020) 2522e2524 Table 3 Values of exergy destruction loss rate and non dimensional exergy loss rate in major components of VAR system. Components
Exergy loss rate (kW) from this study
Non dimensional exergy loss (%) from this study
Generator Condenser Evaporator Absorber HEX Total
1.373 1.580 0.051 0.240 0.329 0.825
166.4 191.370 6.176 28.986 39.869 100
Proposed corrections: In this section, authors have estimated the exergy loss rate in major components of VAR system using incorrect values of specific exergy [1] and presented Table 2. Final Corrections: Authors have estimated corrected values for specific exergy at each thermodynamic state of VAR system, exergy loss rate and non dimensional exergy loss rate in major components of VAR system using correct mathematical expressions of exergy loss rate in generator. This estimation is presented in Table 3. 6. Conclusion Authors have found essential discussion opportunity to improve the results and formulation of mathematical expressions in the published work. Linghui Zhu and Junjie Gu must edit the mathematical expression for exergy loss rate in generator, specific exergy at each thermodynamic states of VAR cycle and the exergy loss rate in major component of VAR system, using author's proposed correction. Results presented from this study are comparative index for validating the research for future researchers on the AmmoniaThiocynate working fluids otherwise incorrect results may misguide the research of future researchers. Nomenclature VAR HEX EV Cp T h s
Vapour Absorption Refrigeration Generator absorber heat exchanger Expansion valve Specific heat (kJ/kg-k) Temperature (k) Specific enthalpy(kJ/kg) Specific entropy(kJ/kg-k)
P
:
Pressure (kPa)
DЕ
Exergy Destruction due to irreversibility (kW)
Q : m e
Heat Transfer Rate (kW) Mass Flow Rate (kg/s) Specific Exergy (kW)
Subscripts 0 A C E G v
Dead State Absorber Condenser Evaporator Generator Vapour
:
References [1] L. Zhu, J. Gu, Second law-based thermodynamic analysis of ammonia/sodium thiocyanate absorption system, Renew. Energy 35 (2010) 1940e1946. [2] L.H. Zhu, S.J. Wang, J.J. Gu, Performance investigation of a thermal-driven refrigeration system, Int. J. Energy Res. 32 (2008) 939e949. [3] E.O. Ataer, Y. Gogus, Comparative study of irreversibilities in an aquaammonia absorption refrigeration system, Int. J. Refrig. 14 (1991) 86e92. [4] Kilic Muhsin, Kaynakli Omer, Second law-based thermodynamic analysis of water lithium bromide absorption refrigeration system, Energy 32 (2007) 1505e1512. [5] A. Sencan, A.K. Yakut, A.S. Kalogirou, Exergy analysis of lithium bromide/water absorption systems, Renew. Energy 30 (2005) 645e657. [6] R. Maryami, A.A. Dehghan, An exergy based comparative study between LiBr/ water absorption refrigeration systems from half effect to triple effect, Appl. Therm. Eng. (2017), 124,103e123. [7] Dheerendra Vikram Singh, Govind Maheshwari, Comment on “Thermodynamic analysis of absorption refrigeration cycles using the second law of thermodynamics method” by S. Aphornratana and I. W. Eames [Int. J. Refrigeration 18(4), 244e252, 1995]”, Int. J. Refrig. 48 (2014) 71e73.
Contents lists available at ScienceDirect
Renewable Energy journal homepage: www.elsevier.com/locate/renene
Thermodynamic discussion on “Second law-based thermodynamic analysis of Ammonia/Sodium Thiocyanate absorption system” by Linghui Zhu and Junjie Gu, Renewable Energy, 35 (2010), 1940e1946 Dheerendra Vikram Singh*, Tikendra Nath Verma National Institute of Technology- Manipur, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A paper has been published in Renewable Energy, second law-based thermodynamic analysis of Ammonia/Sodium Thiocynate vapour absorption refrigeration (VAR) system. Linghui Zhu and Junjie Gu have done exergy analysis and estimated exergy loss rate using second law analysis under different headings. The present paper attempts to discuss and comments on the calculation procedure, calculated results and mathematical expressions of the past published work of Linghui Zhu and Junjie Gu. Authors have also presented correction against each comment which must be used by future researchers. This study is the appropriate corrigendum for the past published work of Linghui Zhu and Junjie Gu. © 2019 Published by Elsevier Ltd.
Keywords: VAR Ammonia/Sodium Thiocynate Exergy analysis
1. Introduction
2. Discussion 1
A paper had been published on Renewable Energy, second lawbased thermodynamic analysis of Ammonia/Sodium Thiocynate absorption system by Linghui Zhu and Junjie Gu in 2010. They [1] have performed exergy analysis under the second law on Ammonia/Sodium Thiocynate operated VAR system. Authors have presented schematic diagram of VAR system which have been used by Linghui Zhu et al. in their analysis. Linghui Zhu et al. [1] have presented procedure of calculation of the thermodynamic properties which have numerous mathematical equations and consists the essential part of their past published work. Linghui Zhu and Junjie Gu have formulated mathematical expressions from fundamental exergy balance equation for estimating exergy loss rate in major components of VAR system and also presented estimated results. Variations in COP (coefficient of performance) & ECOP (exergetic coefficient of performance) are also depicted with variations in temperature of different components. Authors have found the essential reasons for discussing specific sections of past published work [1] and authors have also proposed the corrections on the discussions. Fig. 1 illustrates the system description which used in past work [1].
Linghui Zhu et al. [1] have presented mathematical expression for predicting the specific heat of superheated ammonia vapour to be used for calculating thermodynamic properties of working fluid. The mathematical expression (23) [1] for this specific heat of superheated ammonia vapour is presented below:
Cp ¼
https://doi.org/10.1016/j.renene.2019.11.041 0960-1481/© 2019 Published by Elsevier Ltd.
di ðT 273:15Þi
(1)
i¼0
This Equation (1) consists of the value of coefficient di and its value is wrongly reported in the published work [1]. Proposed correction: it is typographical mistake and its correct value is 1.7767 instead of 1.7467.
3. Discussion 2 In subsection 2.2 [1], mathematical expressions for estimating exergy loss rate in major components of VAR system have formulated under equation (26) to (30) [1] which have presented below: :
DOI of original article: https://doi.org/10.1016/j.renene.2019.09.097. * Corresponding author. E-mail address: [email protected] (D.V. Singh).
6 X
:
:
:
:
DЕG ¼ m8 E8 m7 E7 m1 E1 þ QG 1
T0 TG
(2)
D.V. Singh, T.N. Verma / Renewable Energy 147 (2020) 2522e2524
2523
exergy of output stream flow in component is taken as negative [2e7]. This work [1] have also obeyed this rule and deduced the mathematical expression for estimating the exergy loss rate in condenser, evaporator, absorber and HEX (Generator absorber heat exchanger) but exergy rate in generator is wrongly formulated. From Fig. 1, stream 7 is entering in generator and stream 1 & 8 are leaving the generator. Therefore correct mathematical expression of exergy loss rate in generator is presented in equation (7). :
:
:
:
:
DЕG ¼ m7 E7 m8 E8 m1 E1 þ QG 1
T0 TG
(7)
4. Discussion 3 Linghui Zhu et al. [1] have presented the values of the specific exergy at each salient point of VAR cycle in their published work [1]. Present work found the discussion opportunity to correct the values of specific exergy at thermodynamic states 1, 2, 8, 9 & 10. Proposed Correction: Fundamental equation of specific exergy is presented in equation (8).
Fig. 1. The schematic of a single stage VAR cycle [1].
:
DЕ
:
: А ¼ m4 E4 þ m10
:
:
:
:
DЕ C ¼ m1 E1 m2 E2 QC 1 :
:
:
:
DЕE ¼ m3 E3 m4 E4 þ QE 1 :
e ¼ ðh h0 Þ T0 ðs s0 Þ
T E10 m5 E5 QA 1 0 TA :
:
:
T0 TC
T0 TE
In this work, for this discussion, the correct values of specific exergy is estimated at each salient thermodynamic state of VAR system and reported in Table 1. The term h and s are specific enthalpy and entropy of fluid at temperature of state while h0 and s0 are the specific enthalpy and specific entropy at dead state and as h0 ¼ 315.88 kJ/kg & s0 ¼ 1.123 kJ/kg-k [1]. Remarkable difference can be observed in the value of specific exergy at the thermodynamic states 1, 2, 8, 9 & 10 from Table 1 very easily.
(3)
(4)
(5)
:
DЕ GAX ¼ m6 ðE6 E7 Þ þ m8 ðE8 E9 Þ
(8)
5. Discussion 4
(6)
Values of exergy destruction in generator & absorber and values of non dimensional exergy loss (%) in major components of VAR system are reported incorrect in Table 2 & Table 3 [1] using incorrect values of specific exergy [1].
In those above following equations, exergy rate in generator is not formulated correctly. Proposed correction: According to formulation principle, exergy of input stream flow in component is taken as positive and Table 1 Values of specific exergy taken from present work and past published work [1]. State
T (0C)
x (%)
:
m (kg/s)
h (kJ/kg)
s (kJ/kg-k)
h0 (kJ/kg)
s0 (kJ/kg-k)
t0 (k)
P (kPa)
e (kJ/kg)
[1] 1 2 3 4 5 6 7 8 9 10
e (kJ/kg) Present Study
90 25 25 10 25 25 67.92 90 38 38
100 100 100 100 0.4618 0.4618 0.4618 0.3843 0.3843 0.3843
0.0038 0.0038 0.0038 0.0038 0.03 0.03 0.03 0.0262 0.0262 0.0262
1689.7 315.88 315.88 1449.5 101.847 101.847 15.767 71.783 62.767 62.767
4.337 1.123 1.123 5.473 0.726 0.726 1.033 1.056 0.747 0.747
315.88 315.88 315.88 315.88 101.847 101.847 101.847 101.847 101.847 101.847
1.123 1.123 1.123 1.123 0.726 0.726 0.726 0.726 0.726 0.726
298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15
1002.6 1002.6 290.76 290.76 290.76 1002.6 1002.6 1002.6 1002.6 290.76
411.979 0 0 ¡166.979 0 0 26.08 52.072 9.62 9.62
415.57 0 0 ¡163.33 0 0 26.082 75.241 32.819 32.819
Table 2 Comparative analysis of exergy & non dimensional exergy loss from present study & past published work [1]. Components
Exergy loss rate (kW) [1]
Exergy loss rate from this study(kW)
Non dimensional exergy loss (%) [1]
Non dimensional exergy loss (%) from this study
Generator Condenser Evaporator Absorber HEX Total
0.4107 1.5655 0.0651 0.3825 0.3299 1.9887
0.411252a 1.5655 0.0648 - 0.38248 0.329842 1.9889
14.91 56.85 2.37 13.89 11.98 100
20.67721 78.7113 3.258059 19.2306 16.58403 100
a This value is also incorrect because it is calculated using wrong mathematical expression which has been presented by Linghui Zhu et al. [1] and its proposed correction has been already given under discussion 2.
2524
D.V. Singh, T.N. Verma / Renewable Energy 147 (2020) 2522e2524 Table 3 Values of exergy destruction loss rate and non dimensional exergy loss rate in major components of VAR system. Components
Exergy loss rate (kW) from this study
Non dimensional exergy loss (%) from this study
Generator Condenser Evaporator Absorber HEX Total
1.373 1.580 0.051 0.240 0.329 0.825
166.4 191.370 6.176 28.986 39.869 100
Proposed corrections: In this section, authors have estimated the exergy loss rate in major components of VAR system using incorrect values of specific exergy [1] and presented Table 2. Final Corrections: Authors have estimated corrected values for specific exergy at each thermodynamic state of VAR system, exergy loss rate and non dimensional exergy loss rate in major components of VAR system using correct mathematical expressions of exergy loss rate in generator. This estimation is presented in Table 3. 6. Conclusion Authors have found essential discussion opportunity to improve the results and formulation of mathematical expressions in the published work. Linghui Zhu and Junjie Gu must edit the mathematical expression for exergy loss rate in generator, specific exergy at each thermodynamic states of VAR cycle and the exergy loss rate in major component of VAR system, using author's proposed correction. Results presented from this study are comparative index for validating the research for future researchers on the AmmoniaThiocynate working fluids otherwise incorrect results may misguide the research of future researchers. Nomenclature VAR HEX EV Cp T h s
Vapour Absorption Refrigeration Generator absorber heat exchanger Expansion valve Specific heat (kJ/kg-k) Temperature (k) Specific enthalpy(kJ/kg) Specific entropy(kJ/kg-k)
P
:
Pressure (kPa)
DЕ
Exergy Destruction due to irreversibility (kW)
Q : m e
Heat Transfer Rate (kW) Mass Flow Rate (kg/s) Specific Exergy (kW)
Subscripts 0 A C E G v
Dead State Absorber Condenser Evaporator Generator Vapour
:
References [1] L. Zhu, J. Gu, Second law-based thermodynamic analysis of ammonia/sodium thiocyanate absorption system, Renew. Energy 35 (2010) 1940e1946. [2] L.H. Zhu, S.J. Wang, J.J. Gu, Performance investigation of a thermal-driven refrigeration system, Int. J. Energy Res. 32 (2008) 939e949. [3] E.O. Ataer, Y. Gogus, Comparative study of irreversibilities in an aquaammonia absorption refrigeration system, Int. J. Refrig. 14 (1991) 86e92. [4] Kilic Muhsin, Kaynakli Omer, Second law-based thermodynamic analysis of water lithium bromide absorption refrigeration system, Energy 32 (2007) 1505e1512. [5] A. Sencan, A.K. Yakut, A.S. Kalogirou, Exergy analysis of lithium bromide/water absorption systems, Renew. Energy 30 (2005) 645e657. [6] R. Maryami, A.A. Dehghan, An exergy based comparative study between LiBr/ water absorption refrigeration systems from half effect to triple effect, Appl. Therm. Eng. (2017), 124,103e123. [7] Dheerendra Vikram Singh, Govind Maheshwari, Comment on “Thermodynamic analysis of absorption refrigeration cycles using the second law of thermodynamics method” by S. Aphornratana and I. W. Eames [Int. J. Refrigeration 18(4), 244e252, 1995]”, Int. J. Refrig. 48 (2014) 71e73.