Scholarly article on topic 'Effect of Mass Recovery on the Performance of Solar Adsorption Cooling System'

Effect of Mass Recovery on the Performance of Solar Adsorption Cooling System Academic research paper on "Environmental engineering"

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Abstract of research paper on Environmental engineering, author of scientific article — K.M Ariful kabir, K.C. Amanul Alam, M.M.A. Sarker, Rifat A. Rouf, Bidyut B. Saha

Abstract The study investigates the effect of mass recovery process on the performance of a conventional two bed solar adsorption cooling system with direct solar coupling mathematically. In an adsorption refrigeration system, the pressure in adsorber and desorber are different. The mass recovery scheme utilizes this pressure difference to enhance the refrigerant mass circulation. Average Cooling Capacity (ACC) and Coefficient of Performance (COP) were calculated by computer simulation to analyze the influences of operating conditions. The results show that the average cooling capacity of mass recovery system is superior to that of conventional system. It is also seen that mass recovery process enhances the overall performances of solar driven chiller and there is an optimum mass recovery time for an adsorption cooling system with direct solar coupling

Academic research paper on topic "Effect of Mass Recovery on the Performance of Solar Adsorption Cooling System"

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Energy Procedía 79 (2015) 67 - 72

2015International Conference on Alternative Energy in Developing Countries and

Emerging Economies

Effect of Mass Recovery on the Performance of Solar Adsorption Cooling System

K.M Ariful kabira*, K.C. Amanul Alamb, M. M. A. Sarkera, Rifat A. Rouf,

Bidyut B. Sahad

aBangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh bEast West University, Dhaka-1214,Bangladesh cIndependent University, Bangladesh, Dhaka-1229, Bangladesh dInterdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-shi, Fukuoka, Japan

Abstract

The study investigates the effect of mass recovery process on the performance of a conventional two bed solar adsorption cooling system with direct solar coupling mathematically. In an adsorption refrigeration system, the pressure in adsorber and desorber are different. The mass recovery scheme utilizes this pressure difference to enhance the refrigerant mass circulation. Average Cooling Capacity (ACC) and Coefficient of Performance (COP) were calculated by computer simulation to analyze the influences of operating conditions. The results show that the average cooling capacity of mass recovery system is superior to that of conventional system. It is also seen that mass recovery process enhances the overall performances of solar driven chiller and there is an optimum mass recovery time for an adsorption cooling system with direct solar coupling

© 2015 The Authors.PublishedbyElsevierLtd. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the Organizing Committee of 2015 AEDCEE Keywords: Adsorption; mass recovery; solar energy; cooling system

1. Introduction

Adsorption cooling system is known to be an environmentally friendly air-conditioning system. As the adsorption cooling system requires a low-grade thermal energy source with minimal electricity, therefore, it could be an alternative to traditional vapor compression systems mostly used in buildings and other

* Corresponding author. Tel.:+ 880-1722852818;Fax:+880-2-8613026 E-mail address: k.ariful@yahoo.com

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the Organizing Committee of 2015 AEDCEE doi:10.1016/j.egypro.2015.11.479

places. Integrating adsorption cooling systems with solar energy or waste heat can substantially reduce the dependency on fossil fuels making them potential candidates for net zero energy building operation [1,2]. Though absorption cycles are predominant in the area of heat driven heat pump/refrigeration technologies, adsorption (solid gas) cycles have some distinct advantages over the other systems in viewpoints of their ability to be driven by relatively low temperature heat source [3]. From this context, extensive investigations on the performances of adsorption refrigeration/heat pump system have been conducted considering various adsorbent/adsorbate pairs. Following are some such examples: Zeolite/ water [4,5], activated carbon/ammonia [6], activated carbon/methanol [7] and silica gel/water [8-10]. Many advanced cycles have been proposed to improve the system performance. Mueiner [11] studied the system performance of cascading cycle in which an activated carbon/methanol cycle topped by zeolite/water. Pons and Poyelle [12] studied the influence of mass recovery process in conventional two beds adsorption cycle. Later, Wang [13] investigated the performances of vapor (mass) recovery cycle with activated carbon-methanol as adsorbent/adsorbate pair and demonstrated that the mass recovery cycle is effective for the low regenerating temperature.

Many researchers studied the adsorption cooling system utilizing solar energy, among them, remarkable studies are made by Pons and Guilleminot [14] and Boubarkri [15] for ice production, Anyanwu and Ogueke [16] and Anyanwu and Ezekwe [17] for refrigeration system, Sumanthy et al.[18], Clauss et al [19] and Alam et al.[20] for air-conditioning system. Recently, Rouf et al. [21] investigated performance of solar driven adsorption chiller for climatic condition of Dhaka, Bangladesh. Later, Alam et el.[22] introduced heat storage tank to the solar driven adsorption cooling system to extend the working hour beyond sunset. As it was discussed that solar driven air-conditioning has a great potential and mass recovery cycle enhances the performance, therefore, solar driven cooling system with mass recovery process will be very effective. From this context, a two bed conventional adsorption cooling system with mass recovery coupled with solar collector, with silica gel-water pair as adsorbent/adsorbate, is analyzed numerically under the climatic condition of Dhaka, Bangladesh in the present study.

Nomenclature Subscript

A area V collector efficiency Cp collector pipe

W weight U heat transfer coefficient Cr collector

C specific heat I solar radiation Chill chill water

T temperature

m mass flow rate

2. Principle and Operational Process of the System

A two- bed mass recovery adsorption cooling system driven by solar heat has been considered. Silica gel-water pair as adsorbent/ adsorbate has been chosen for the present study.

CPC Solar collector

Condenser

-EvaporatoL

-V Cooling 7

SE2 v9. SE1 ! -« 1 v3 1 Outdoor Unit

Vio - 1 V4

Chilled water

Fig.1. Schematic diagram of the solar driven adsorption cooling system with mass recovery.

There are six thermodynamic steps in the cycle, namely, (i) Pre-cooling (ii) Adsorption/Evaporation (iii) Mass recovery with cooling (iv) Pre-heating (v) Desorption/ Condensation and (vi) Mass recovery with heating. No heat recovery is considered in the present study. The adsorber (SE1/SE2) is alternately connected to the solar collector to heat up the bed during pre-heating and desorption/ condensation process and to the cooling tower to cool down the bed during pre-cooling and adsorption/ evaporation process. The heat transfer fluid transport heat from the solar collector to the desorber and returns to the collector to regain heat from the collector. The valve between adsorber and evaporator and the valve between desorber and condenser are closed during pre-cooling/ pre-heating period while, these are open during adsorption/evaporation and desorption/ condensation process. At the end of adsorption/evaporation and desorption/condensation process the valves V5 and V8 are closed and the valve V10 (between SE1 and SE2) is now open for mass recovery mode. Mass recovery process can also be called as an 'internal vapour recovery processes'. At the start of mass recovery, the heated adsorber has high pressure while the cooled adsorber has low pressure. By connecting the two adsorbers together, the water vapour will flow from the high pressure heated adsorber to the low pressure cooled adsorber. According to the pressure differences in the adsorbers, adsorption/desorption process will occur automatically without applying any heating and cooling. Thus, the desorbed water vapour from heated adsorber will move to the cooled adsorber.

The schematic of the adsorption cooling with solar collector panel with mass recovery is presented in Fig.1. A detailed description of solar collector driven adsorption cooling system is available in Alam et al. [20] and mass recovery cycle is available in Akahira et al. [23].

3. Mathematical Modelling

In the present study, lumped parameter model has been exploited. The temperature and pressure are uniform throughout the whole adsorber. The simulation procedure is elsewhere available in Alam et al [20].

The heat transfer fluid is equally distributed to all the collectors and the combined outlet from all the collectors then enters into desorber. Each collector has nine pipes, water enters through the first pipe and the outlet of the first pipe enters into the next pipe thus the outlet of the ninth pipe of each collector combines together and enters into the desorber. Hence the temperature of the heat transfer fluid in each pipe is calculated separately for all the collectors. The energy balance of each collector can be expressed as [24]:

WcPiiCcr ^ = y{riiAcriI + mfcrCf(Tcr^in — Tcr^outy} + (1 — Y)UlossAcri(Tam — Tcr{) (i)

Tcr,i,out r^cr,i ^ (Tcr,i,in Tcrti)EXP(UcpAcPti/mftCrCf) (2)

The collector efficiency equation is considered to be same as Clauss et al. [19]. The cyclic average cooling capacity (CACC), the cycle COP (coefficient of performance) and solar COP in a cycle are calculated respectively by the equations,

end of cycle time

CCC^ / (w-w)^ (3)

begin of cycle time

rend of cycle time . „ ^ ,

Jbeginof cycle timemCWcP,Cw{1 CW,in ~ 'cw,out)dt

cVcle rend of cycle time . r _ „ \ , (4)

Jbeginof cycle tirnemHwCp'HwylHW'out lHW,in)at

rendofcycletíme . „ _

JbegínofcycletímemCWLP,CwVcw,ín lCW,outJal

C0PSC jendofcycletime ^ (5)

Jbeginofcycletime L'

Where, I is the solar irradiance, Arr is each collector area and n is number of collectors.

4. Results and Discussions

The intension of the present study is to enhance cooling capacity, the mass recovery process is considered for a conventional two bed adsorption chiller with direct solar coupling. For the climatic condition of Dhaka at least 14 collectors with 1000s cycle time is needed [21] for a conventional two bed with silica gel water pair the basic adsorption chiller with baser run conditions. The temperature histories of the adsorption beds with and without mass recovery process are depicted in Fig.2. In case of direct solar coupling with cycle time 1000s, the bed temperature reaches 87°C, however, the temperature rises around 84°C with 60s mass recovery time. It is also seen that increasing mass recovery time produces lower bed (desorber) temperature for the same cycle time. This is due to the mass recovery scheme. As the desorber releases more vapor during the mass recovery process; therefore, hot bed releases more heat as a result of adsorption/desorption characteristic.

Though the bed temperature for without mass recovery cycle is higher than that of mass recovery cycle, better cooling capacity is observed for mass recovery cycle. The cooling capacities without mass recovery process and with different mass recovery process time are compared in Fig. 3.It is seen that increasing mass recovery process time does not affect the cooling capacity. As, optimum adsorption and desorption capacity of silica gel is limited, once saturated enhanced time of mass recovery does not help in more uptake, therefore, there is no further improvement in cooling capacity. Thus, it may conclude that there is an optimum mass recovery process time for the base run conditions. For the present case the optimum mass recovery process time is 60s. It is also seen that mass recovery process for an adsorption chiller with direct solar coupling enhances the working hour at the steady state (3rd day). As mass recovery process improve the cooling capacity, therefore, it may be predicted that the collector area could be reduced by introducing mass recovery process in solar driven cooling system which need a further detail investigation.

-without mass recovery mass recovery 60s -mass recovery 100s -mass recovery 200s

-without mass recovery -mass recovery 60s mass recovery 100s -mass recovery 200s

12.1 12.2 12.3

Day Time (Hour)

Fig. 2.Temperature profile for beds of different mass recovery times.

Without Mass Recovery ■ Mass recovery 60s

Mass Recovery 100s • Mass Recovery 200s

10 12 14

Day Time (Hour)

Fig. 3. Cooling capacity (KW) of different mass recovery times.

8 10 12 14 16 18

6 8 10 12 14 16 18

Day Time (Hour)

Day Time (Hour)

Fig.4. Solar COP in a cycle for mass recover (60s) and without mass recovery

Fig.5. Cycle COP in a cycle for mass recover (60s) and without mass recovery

The solar COP in cycle (COPsc) and thermal COP in a cycle (COPcycle) are presented respectively in

Fig.4 and Fig.5. It is seen that both COP values are improved if mass recovery process is applied. It is

also seen that the improvement rate in early morning and late afternoon is higher than those in mid-day.

As the mass recovery cycle works effectively with relatively low temperature heat source (Akahira et al.

[23]), therefore, the system shows better COP values in the morning and at late afternoon.

5. Conclusion

Based on the analysis of the mass recovery process with the solar heat driven adsorption chiller with

direct solar coupling, the following concluding remarks can be made for the base run conditions.

• Mass recover process enhances the performances of the solar driven adsorption chiller. Mass recovery process also enhances the working hour.

• The optimum mass recovery time is 60s.

• Maximum Cyclic average cooling capacity with mass recovery is around 11.45 kW at noon while the system produces around 10.5kW without mass recovery process at the same time. Therefore, almost 9% cooling capacity can be achieved by introducing mass recovery

• Finally, it may be concluded that the number of collector may be reduce by employing mass recovery process which has to be investigated.

Acknowledgments

The authors wish to acknowledge the technical and financial support provided by the Independent

University, Bangladesh (IUB) and Bangladesh University of Engineering and Technology (BUET).

[1] Tso C.Y., Chao C.Y.H., Fu S.C., Performance analysis of a waste heat driven activated carbon based composite adsorbent-water adsorption chiller using simulation model, Int.J.Heat Mass Tran. 55(2012) 7596-7610.

[2] Alam K.C.A, Akahira. A., Y. Hamamoto, Akisawa. A., Kashiwagi.T., A four-bed mass recovery adsorption refrigeration cycle driven by low temperature waste/renewable heat source, Renew Energy. 29 (2004) 1461-1475.

[3] Kashiwagi T, Akisawa A, Yoshida Y, Alam K.C.A, Hamamoto Y. Heat driven sorption refrigerating and air conditioning cycle in Japan. In: Proceedings of the International Sorption Heat Pump Conference, 24-27 September 2002, Shanghai, China. p. 50-62.

[4] Karagiorgas M, Meunier F. The dynamics of a solid adsorption heat pump connected with outside heat sources of finite capacity. J Heat Recovery Systems CHP 1987; 7(3):285-99.

[5] Tchemev D.I., Emerson D.T.E. High efficiency regenerative zeolite heat pump. ASHRAE Trans 1988;94(2):2024-32

References

[6] Critoph R.E., Vogel R. Possible adsorption pairs for use in solar cooling. Int J Ambient Energy 1986; 7(4):183-90.

[7] Critoph RE. Activated carbon adsorption cycles for refrigeration and heat pumping. Carbon 1989;27:63-70.

[8] Saha B.B, Boelman E.C, Kashiwagi T. Computer simulation of a silica gel-water adsorption refrigeration cyclethe influence of operating conditions on cooling output and COP. ASHRAE Trans Res 1995;101(2):348-55.

[9] Chua H.T., Ng KC, Malek A, Kashiwagi T, Akisawa A, Saha B.B. Modeling the performance of two-bed, silica gel-water adsorption chillers. Int J Refrigeration 1999; 22: 194-204.

[10] Alam K.C.A., Saha B.B., Kang Y.T, Akisawa A, Kashiwagi T. Heat exchanger design effect on the system performance of silica gel-water adsorption system. Int. J Heat and Mass Transfer 2000;43(24):4419-31.

[11] Meunier F. Theoretical performances of solid adsorbent cascading cycles using the zeolite-water and active carbonmethanol pairs: four case studies. Heat Recovery CHP systems 1986;6(6):491-8.

[12] Pons M, Poyelle F. Adsorptive machines with advantaged cycles for heat pumping or cooling applications. Int J Refrigeration 1999; 22:27-37.

[13] Wang R. Z. Performance Improvement of Adsorption Cooling by Heat and Mass Recovery Operation. Int J Refrigeration 2001; 24:602-11.

[14] Pons M, Guilleminot J.J., Design of an experimental solar powered, solid adsorption ice maker, Journal of Solar Energy and Engineering, (Trans. ASME), 103 (4) (1986) 332-337.

[15] Boubakri A., A new conception of an adsorptive solar powered ice maker, Renewable Energy, 28 (2003) 831-842.

[16] Anyanwu E.E., Ogueke N.V., Transient analysis and performance prediction of a solid adsorption solar refrigerator, Applied Thermal Engineering, 27 (2007) 2514-2523.

[17] Anyanwu E.E., Ezekwe C.I., Design, construction and test run of a solid adsorption solar refrigerator using activated carbon/methanol as adsorbent/adsorbate pair, Energy Conversion and Management 44 (18) (2003) 2879-2892.

[18] Sumathy K., Yong Li, Steinhagen H. Muller, Kerskes H., Performance analysis of a modified two-bed solar-adsorption air-conditioning system, Int. J. Energ. Res. 33 (2009) 675-686.

[19] Clausse M., Alam K. C. A., Meunier F., "Residential air conditioning and heating by means of enhanced solar collectors coupled to an adsorption system," Solar Energy, vol.82 (10), pp. 885-892, 2008.

[20] Alam K. C. A., Saha B. B. and Akisawa A., Adsorption cooling driven by solar collector: a case study for Tokyo solar data, Applied Thermal Engineering, 50 (2) (2013) 1603-1609.

[21] Rouf R. A, Alam K. C. A, Khan M. A. H, Ashrafee T. and Anwer M, "Solar Adsorption Cooling: A Case Study on the Climatic Condition of Dhaka", Academy Publisher Journal of Computers,v.8,no 5,pp.1101-1108,2013.

[22] Alam K. C. A., Rouf R. A., Saha B B., Khan M. A. H. and Meunier F."Autonomous Adsorption Cooling — driven by Heat Storage Collected from Solar Heat", Journal of Heat Transfer Engineering (under review).

[23] Akahira A., Alam K.C.A., Hamamoto Y., Akisawa A. and Kashiwagi T., "Mass recovery adsorption refrigeration cycle— —improving cooling capacity", International Journal of Refrigeration, Vol.27, pp.225-234, (2004).

[24] Rouf R. A, Alam K. C. A, Khan M. A.,SahaB B.,MeunierF., Alim. M. A and Kabir. K .A. "Advancement of solar Adsorption Coolin by means of heat storage ", Procedia Engineering v. 90, pp.649-656, 2014.