Online Version ISSN: 1314-412X Volume 5, Number 1 March 2013
2013
Editor-in-Chief Tsanko Yablanski Faculty of Agriculture Trakia University, Stara Zagora Bulgaria Co-Editor-in-Chief Radoslav Slavov Faculty of Agriculture Trakia University, Stara Zagora Bulgaria Editors and Sections Genetics and Breading Atanas Atanasov (Bulgaria) Ihsan Soysal (Turkey) Max Rothschild (USA) Stoicho Metodiev (Bulgaria) Nutrition and Physiology Nikolai Todorov (Bulgaria) Peter Surai (UK) Zervas Georgios (Greece) Ivan Varlyakov (Bulgaria) Production Systems Dimitar Pavlov (Bulgaria) Dimitar Panaiotov (Bulgaria) Banko Banev (Bulgaria) Georgy Zhelyazkov (Bulgaria) Agriculture and Environment Georgi Petkov (Bulgaria) Ramesh Kanwar (USA) Product Quality and Safety Marin Kabakchiev (Bulgaria) Stefan Denev (Bulgaria) Vasil Atanasov (Bulgaria) English Editor Yanka Ivanova (Bulgaria)
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Volume 5, Number 1 March 2013
Online Version ISSN: 1314-412X
2013
AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 5, No 1, pp 58 - 61, 2013
Study of a zeolite–water experimental refrigeration module intended for animal raising R. Georgiev*, K. Peichev, A. Pavlov, K.Trendafilov, G. Dineva, I. Binev Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria Abstract. A laboratory adsorption cooling module was developed. The module is designed to operate on ecological materials: zeolite and water. The authors of this publication set the following objectives: designing and construction of a fully functioning adsorption refrigeration module thermally powered by a solar collector system and study of the dynamics of temperature parameters defining the cooling and condensation processes in the adsorption refrigeration module. Its potentials for cooling (air conditioning) were investigated. In the zone of the evaporator, refrigerant temperatures in the range of 1–5 °C were obtained for 6.5 hours. During cooling (adsorption) temperature of the zeolite rose by 8.5 °C. For desorption of water vapour (refrigerant) heat from thermal solar systems 78÷80 °С was used.
Keywords: solar energy, cooling, zeolite-water
Introduction
T
The interest in adsorption cooling systems has aroused since the last energy crises. The use of alternative energy such as waste heat or solar energy to drive such systems became a priority for many research groups (Eicker, 2002; Grossman, 2002; Wang, 2005). Non-ecological refrigerants containing CFCs and HCFCs were limited in 1990 as when released into the atmosphere they make the ozone layer thinner and contribute to the greenhouse effect. This gave impetus to the use of green refrigerants such as water (water vapour) (Maier-Laxhuber, 1990; Ramos, 2003). The use of moisture adsorbent material such as zeolite is quite appropriate because it is common in nature (Baog, 2001). This prompted the authors to construct a laboratory zeolite-water module driven by heat from solar energy. In line with the above concept, the authors of this publication set the following objectives: development of a theoretical model of a cooling system of the adsorption type with thermally powered work processes; designing and construction of a fully functioning adsorption refrigeration module thermally powered by a solar collector system; study of the dynamics of temperature parameters defining the cooling and condensation processes in the adsorption refrigeration module.
Material and methods A schematic drawing of the theoretical adsorption cooling module is shown in Figure 1.The operating agent of the refrigeration module is distilled water which phase transformation occurs in a vacuum medium with an initial value of the residual pressure Premaining = 600 Pa. The cycle of heat transfer occurs in two processes – adsorption (evaporation) and desorption (condensation). Water boils at a temperature of about 1–2 °C at the account of the external heat in the cooled medium 9 and vacuum in the evaporator. Released vapours enter the adsorber 1 where they are absorbed by * e-mail:
[email protected]
58
4 3 T V T 1
6 2
7
5 V T T
10
9 8 V T
- Vacuum meter and thermometer
T
- Thermometer 1 2 3 4 5
– – – – –
adsorber; 6 heating coil; 7 circulation pump; 8 heat source; 9 condenser; 10
– – – – –
condenser bath; control valve; evaporator; cooling vessel; vacuum pump
Figure 1. Schematic drawing of an adsorption refrigeration machine
a surface-active medium. As such is used zeolite containing the active substance clinoptilolite of concentration at humidity .2 adsorption medium parameters are certified . The cooling process is considered completed hen the temperature of the evaporator and the remaining ater in it e ceeds C, i.e. t , and the temperature of the vapours discharged to the adsorber C, i.e. t , respectively. At this point, the residual absolute pressure in the system reaches 2 kPa. The process of desorption and condensation starts ith the provision of thermal energy from an e ternal source. or this purpose, the heat-transfer medium ater of an appro imate temperature C is fed forcedly from the heat e changer vessel by circulation pump to the heating coil 2 of the adsorber . This temperature regime is consistent and functionally related to the performance parameters of a solar collector system ith selective type panels. Heating for desorption occurs at atmospheric conditions hich ensures complete safety for the operation of the heat source . Under these conditions zeolite is heated to a temperature of appro imately C, hile the temperature of desorbing vapours reach 2 C. Vapours discharged from adsorber enter condenser here they become li uefied at the account of the heat released. The condensation phase of the refrigerant distilled ater flo s into the evaporator by gravity. Upon completion of the desorption and condensation process the pressure in the system reaches kPa. After s itching off the circulating pump and termination of e ternal heat transfer to coil 2 of adsorber , the orking cycle is repeated in the se uence described. The vacuum mode of the system at initial operation is provided by vacuum pump installed in the piping bet een evaporator , adsorber and condenser . The flo rate of the connections bet een the elements of the module is finely ad usted by control valve . On the basis of this conceptual model, design solutions ere implemented defining the heat transfer processes in the course of the ork cycle and conse uently the follo ing as determined capacity of adsorber and uantity of zeolite heat e change surface of the adsorber coil heat e change surface and rating of condenser capacity of evaporator and eight of refrigerant distilled ater diameter of piping connecting the components of the system. Temperature regime of the e ternal heat source as assumed a priori in the range of C in accordance ith the average temperature potential of solar collector plants. After a comprehensive analysis of the results, a fully functioning adsorption refrigeration module as designed and built. A general vie of the module is sho n in igure 2. The follo ing ork process parameters ere e perimentally controlled and monitored by means of thermal and manometric measurement e uipment absolute residual pressure ithin the adsorption module, temperature in the adsorber t , temperature of ater vapours refrigerant after evaporator
t , temperature of boiling refrigerant
temperature of
evaporator t , temperature of condensation t2 , temperature of e ternal heat transfer medium t , ambient temperature t , .
Figure 2. A general view of the experimental system.
During the e perimental study of the cooling module the temperature dynamics of refrigerant vapours t and boiling phase t ere e amined. The identified variations are described by the follo ing functions t f T, t f T, here is duration of cycle of registered temperature values, min.
Results and discussion The development and e perimental study of this adsorption cooling module took place at the Technical acility Centre of the Agricultural Engineering Department, aculty of Agriculture, Trakia University. A total of 2 observations ere conducted in different calendar days in ebruary and March 2 2 , of single duration of . hours. Registration of the studied variables as done at every minutes in the course of the e periment. The charts in igure are plotted on the basis of the average values of variables measured at the timing points. The dynamics of the temperature variation of ater vapours t and temperature of boiling refrigerant t as nearly identical in the first 2 hours of the e periment. The value of both variables dropped from . C to . C. After the th minute of the observations an opposite trend for both studied temperatures as reported. The value of the boiling refrigerant t continued ith its decline and to ards the end of th hour 2 th-2 th minute from the beginning of adsorption the minimum in the range of . to .2 C for the duration of the 59
t,oC 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
t3
tA t4
tl4 , min 0
30
60
90
120
150
180
210
240 270
300
330 360
390
420
450
Figure 3. Temperature variation during the experiment.
experiment was recorded. In the same period the temperature of water vapours (t4) showed a positive change. For the interval from the 130th to 250th minute of the experiment its value rose from 3.8 to 6.0 °C. At the fifth hour of observations the two temperatures showed an instantaneous temperatures rise, from 5 °C to 7 °C for t4 and from 1.5 °C to 2.5 °C for t׳4 respectively, then dropped again to levels of 5 °C for t4 and 1.2 °C for t׳4. The probable reason for the variations reported is an accidental ambient temperature change which was not considered as a systematic factor in the experiment. At higher ambient temperatures, the temperature of evaporator t׳4 is expected to be higher (Svoboda, 2012). After the 330th minute of observations the values of the two variables started to rise almost at a similar positive acceleration and at the 7th hour from the beginning of the experiment they reached the same level of 10 °C. The described dynamics of the studied variables was manifested in almost constant temperature conditions of the experiment. The graph shows that ambient temperature changed from 9 °C at the beginning of the experiment to 12 °C at its end. Most probably, the three degrees of positive temperature rise is the cause for the final variable values (10 °C at the 450th minute) to be 1 °C higher than those in the first minutes of the experiment (t4 ≈ t׳4 ≈ 8, 5°С). Irrespective of the available temperature fluctuations, the overall trend of the temperature of the boiling refrigerant (water) t׳4 and this of the water vapours t4 allows to formulate two main conclusions. The process of vapour adsorption by boiling distilled water under the conditions of deep vacuum (Раbc ≈ 600Ра) allows to reach temperature levels of about 1.5 to 5 °C in the area of the evaporator. The values measured provide an exceptionally good opportunity for technologization and use of adsorption refrigeration modules as air-conditioning systems in the field of industrial animal raising. 60
The process of adsorption and cooling as related to the design parameters of the demonstrated module is of approximate duration of 6.5 hours, which is a good possibility to control peak temperatures in livestock buildings in the midday and early afternoon hours. The graph in Figure 3 shows also the dynamics of temperature in the refrigeration module adsorber – t3. With some fluctuations, it increased its value from 8.5 °C at the beginning of the experiment to levels of 15 –17 °C reached at the third hour of observations. From this point of measurements (around the 180th minute to the end of measurements) the temperature of adsorption was almost constant at levels of about 17.0–17.5 °C. The positive temperature difference between the values t3 andtА is the result of the exothermic processes co-occurring with the adsorption of water vapours. Within the context of the findings the measurement taken at 330th minute of the experiment was assumed as the end of the refrigeration process (adsorption process). The next placing of the module in cooling mode involves desorption of water vapour by zeolite and subsequent condensation to the evaporator. The running of these two processes requires the use of energy from an external heat source and release of condensation heat in the environment.
Conclusion The method of adsorption of water vapours under the conditions of deep vacuum can be technologized and used to generate cold. Zeolite can be used as an adsorbent of water vapours. Temperatures obtained in the evaporator of this fully functioning adsorption module are exceptionally suitable for its use as an air-conditioning machine for industrial animal raising applications. Desorption of the refrigerant (water vapours) and repeated placing of the module in cooling mode can be realized
using solar heat energy or other process waste heat flows of temperatures 75–80 °C.
References Baog H, Hongyen Y, Dequan Y and Guoxi L, 2001. Utilization of nature zeolites for solar energy storage. Paper 9404, Changchun, Jilin Province, 130118, China. Eicker U, 2002. Entwieklungstendenzen Solarthermischer Kuhlverfaren, In: Tagungsband Zweites Simposium – Solares Kuhlen in der Praxis. Veroffentlichungen der Fachhochschule Stuttgart-Hochschule für Technik, 56, 2002, S, 6-16. Grossman G, 2002. Solar-powered systems for cooling,
dehumidification and conditioning, In: Solar Energy 72, 2002, 1, 5362. Maier-Lux H, 1990. Zeolite-Water Adsorption Cooling/Heating, US Patent, 492 4676. Ramos M, Espinoza RL, Horn MJ and Fereira AP, 2003. Evaluation of a zeolite-Water solar adsorption refrigerator, Solar World Congress, June 14-19, 2003, Goteborg, Sweden. Wang RZ and Oliviera RG, 2005. Adsorption refrigeration – an efficient way to make good use the waste heat an solar energy, International Sorption Heat Pump Conference, June 22-24, 2005, Denver, CO, USA. Svoboda N, Reind M, Shrager M, Thompson J, Tao C and Rukundo E, 2012. Zeolite Cooling System, University of California, Davis, D-Lab Spring 2012.
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AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 5, No 1, 2013
CONTENTS
1/3
Review Status of remote hybrids in the Poaceae: problems and prospects H. Stoyanov*
3
Genetics and Breeding Genetic divergence among accesions of coriander (Coriandrum sativum L.) N. Dyulgerov, B. Dyulgerova
13
Yield stability of contemporary Bulgarian winter wheat cultivars (Triticum aestivum L.) in Dobrudzha P. Chamurliyski, N. Tsenov
16
Assessment of initial material for stevia (Stevia rebaudiana B.) breeding Tz. Kikindonov
22
Grain yield of winter feed barley varieties B. Dyulgerova, D. Dimova, D. Valcheva, D. Vulchev, T. Popova, M. Gocheva
25
A study on the biological and economic qualities of common winter wheat (Triticum aestivum L.) I. Stankov, S. Tsvetanov, P. Stankova, I. Yanchev, T. Raycheva
28
Nutrition and Physiology Drought–induced changes in photosynthesis of young cowpea plants K. Uzunova, Z. Zlatev
32
Effect of organic fertilizers on photosynthesis of young tomato plants (Lycopersicon esculentum Mill.) Z. Zlatev, V. Popov
35
Production Systems Productivity of sunflower grown in a periodic water deficit conditions R. Petrova, A. Matev, H. Kirchev, A. Sevov
39
Variation of capillary rise of water in the slightly leached chernozem soil of Dobrudzha region under the effect of long-term use of some soil tillage practices P. Yankov
46
Influence of the variety and sowing rate on the green mass productivity of Sudan grass and Sorghum x Sudan grass hybrids Tz. Kikindonov, S. Enchev, K. Slanev
50
Effect of the irrigation regime on the productivity of root celery by drip irrigation in the Plovdiv region B. Harizanova-Petrova, A. Ovcharova
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CONTENTS
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Study of a zeolite–water experimental refrigeration module intended for animal raising R. Georgiev, K. Peichev, A. Pavlov, K.Trendafilov, G. Dineva, I. Binev
58
Method for rapid determination of the percentage rate of grain losses by the combine harvester according to its parameters N. Delchev, K. Trendafilov
62
Phase–frequency characteristics of three types of milking clusters with a different volume and shape of the pulsation chamber B. Banev, K. Peychev, V. Vlashev, G. Dineva
65
Nondestructive (NIRS) determination of some technological traits of Bombyx mori L. cocoons M. Panayotov, S. Atanassova, S. Petrova
70
Researching the resistance of bees fattened up with additive of extract of Tribulus terrestris L. during wintering I. Hristakov, I. Zhelyazkova, V. Hvarchilkov
75
Influence of liming with Ca(OH)2 on nitrogen, phosphorus and potassium content in foliage of vine varieties K. Trendafilov, V. Valcheva, S. Todorova
79
Content and composition of the essential oil of Rosa alba L. during flower development A. Dobreva, M. Gerdzhikova
83
Effectiveness of application of the leaf–fertilizers Hortigrow in sweet basil (Ocimum basilicum var. glabratum) V. Ivanov, I. Yanchev, T. Raycheva, K. Stoyanov
86
Agriculture and Environment A study of macromycetes in Maglenishki Rid, Eastern Rhodopes Mts. II. Recent data of study M. Lacheva
91
Agroclimatic conditions of existence of almond trees in Plovdiv region during the winter period D. Ivanova, N. Shopova
96
Phytoplankton growth and chlorophyll – a content in the surface layer of the Bulgarian Black Sea coastal waters in 2011 D. Petrova, D. Gerdzhikov
99
Ecological status of Varna Bay through the state of phytoplankton, macrozoobenthos and macrophytes during the autumn of 2011 D. Petrova, E. Petrova, D. Gerdzhikov, V. Vachkova, R. Bekova
105
Environmental studies of the macrozoobenthos in the nearby coastal zone along the Bulgarian Black Sea coast E. Petrova, S. Stoykov
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CONTENTS
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Product Quality and Safety Evaluation of pork meat quality and freshness using colorimetric and spectral methods S. Atanassova, T. Stoyanchev, S. Ribarski
115
Reducing the hyperspectral feature spaces of ready-to-cook minced meat products K. Kolev
121
Effect of cold storage terms on physico-chemical characteristics of Japanese quail (Coturnix coturnix japonica) meat S. Ribarski, A. Genchev, S. Atanasova
126
The flavonoid content in the white oil–bearing rose (Rosa alba L.) A Dobreva, M Gerdzhikova
134
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Volume 5, Number 1 March 2013
