Design of a new solar dryer system with swirling flow for drying seeded grape

In this study solar energy supported, swirling flow new drying system is designed and artificial drying of grapes grown around Elazığ/Turkey is investigated. With the developed swirling flow dryer with airy solar collector it is examined that drying occurs homogenously and lower moisture values are obtained in when compared with classical drying system. Also it is found that with an increase in the drying air velocity decreases drying time. When air directing elements are placed inside drying chamber and rotating element to the entrance, it is examined that drying time gets shorter compared to that of natural drying. Thus, drying time which is 200 h in natural conditions decrease to 80 h with an air velocity of 1.5 m/s with the developed solar energy supported swirling flow dryer.     

Aquifer thermal storage (ATES) for air-conditioning of a supermarket in Turkey

A heating, ventilation and air-conditioning (HVAC) system with integrated aquifer thermal energy storage (ATES) was designed for a supermarket building in Mersin, a city near the Mediterranean coast in Turkey (36° 49′ N and 34° 36′ E). This is the first ATES application carried out in Turkey. The peak cooling and heating loads of the building are 195 and 74 kW, respectively. The general objective of the system is to use the groundwater from the aquifer to cool down the condenser of the HVAC system and at the same time storing this waste heat in the aquifer. Cooling with groundwater at around 18 °C instead of utilizing outside summer air at 30–35 °C decreases consumption of electrical energy significantly. In addition, stored heat can be recovered when it is needed in winter. The HVAC system with ATES started operation in August 2001 in cooling mode with an average coefficient of performance (COP) of 4.18, which is almost 60% higher than a conventional system.     

Development of a metal hydride refrigeration system as an exhaust gas-driven automobile air conditioner

Aiming at developing exhaust gas-driven automobile air conditioners, two types of systems varying in heat carriers were preliminarily designed. A new hydride pair LaNi_4.61Mn_0.26Al_0.13/La_0.6Y_0.4Ni_4.8Mn_0.2 was developed working at 120–200 °C/20–50 °C/−10–0 °C. P-C isotherms and reaction kinetics were tested. Reaction enthalpy, entropy and theoretical cycling coefficient of performance (COP) were deducted from Van’t-Hoff diagram. Test results showed that the hydride pair has flat plateau slopes, fast reaction dynamics and small hystereses; the reaction enthalpy of the refrigeration hydride is −27.1 kJ/mol H₂ and system theoretical COP is 0.711. Mean particle sizes during cycles were verified to be an intrinsic property affected by constitution, heat treatment and cycle numbers rather than initial grain sizes. Based on this work pair, cylindrical reactors were designed and a function proving metal hydride intermittent refrigeration system was constructed with heat conducting oil as heat source and water as heat sink. The reactor equivalent thermal conductivity is merely 1.3 W/(m K), which still has not meet practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power is 84.6 W at 150 °C/30 °C/0 °C with COP being 0.26. The regulations of cycling performance and minimum refrigeration temperature (MRT) were determined by altering heat source temperature. Results showed that cooling power and system COP increase while MRT decreases with the growth of heat source temperature. This study develops a new hydride pair and confirms its application in automobile refrigeration systems, while their heat transfer properties still need to be improved for better performance.     

A hybrid solar-assisted adsorption cooling unit for vaccine storage

A concept of a hybrid adsorption cooling unit for vaccine storage utilizing solar energy as a main power supply and a gas burner as an alternative power supply has been developed. The components of the cooling unit have been designed to work under the weathering conditions of Burkina Faso, West coast of Africa according to the requirements of the World Health Organization. For the first adsorber, which is driven by a gas burner, zeolite-13X has been selected. For the second adsorber to be driven by solar energy selective water sorbent SWS-2L has been applied. Water is selected as a refrigerant for both adsorbents. Theoretical investigations of the expected performance of the designed cooling unit have shown a coefficient of performance (COP) of 0.28 for the solar-operated system based on the heat input to the adsorption unit, at the design conditions of T_evap=−5 °C, T_con=55 °C, T_ads=38 °C, T_des(max)=122 °C. For the gas-heated system, also a COP of 0.28 has been estimated at the design conditions of T_evap=−5 °C, T_con=55 °C, T_ads=38 °C, T_des(max)=280 °C. The variations of COP, cooling capacity and the heating power required to operate both systems have been estimated for a broad range of desorption temperatures. It turns out that the SWS-2L/water system is much more sensitive to the operating conditions than the zeolite-13X/water system. The obtained results should serve in designing both control and heating components of the cooling unit.     

Design and performance prediction of a novel double heat pipes type adsorption chiller for fishing boats

A novel double heat pipe type adsorber, which uses compound adsorbent of CaCl₂ and expanded graphite to improve the adsorption performance, is designed. The double heat pipes are integrated into the adsorbers in order to solve the problem of the corrosion between seawater and the steel adsorber in ammonia system and improve the heat transfer performance of the adsorber. There are two kinds of heat pipes integrated with the adsorber. One is the split type heat pipe for heating the adsorber in desorption phase, the other one is the two-phase closed thermosyphon heat pipe for cooling the adsorber in adsorption phase. The performance of two-adsorber adsorption chiller integrated with double heat pipes is predicted. The heat transfer performance of the heat pipes can meet the heat demands for adsorption/desorption of the adsorbent when the heating/cooling time is 720 s and mass recovery time is 60 s. When the exhaust gas temperature is 550 °C, the cooling water temperature is 25 °C, the inlet and outlet chilled water is −10 and −15.6 °C, respectively; the simulation results show that the cooling power and COP of this adsorption system are 5.1 kW and 0.38, respectively.     

Experimental evaluation of a single-stage heat transformer used to increase solar pond’s temperature

A heat source at temperatures not higher than 80°C was used to simulate the heat input to an absorption heat transformer from a solar pond. An experimental absorption heat transformer operated with the water/Carrol mixture was used to demonstrate the feasibility of these systems to increase the temperature of the heat obtained from the solar ponds. Carrol™ is a mixture of LiBr and ethylene glycol [(CH₂OH)₂] in the ratio 1:4.5 by weight. Flow ratios, gross temperature, useful heat, and coefficients of performance are plotted for the heat transformer versus temperature and solution concentration. Gross temperature as high as 50°C were obtained. The maximum temperature of the useful heat produced by the heat transformer was 132°C. The COP for the unit was in the range 0.14–0.36.     

Experimental studies on bubble pump operated diffusion absorption machine based on light hydrocarbons for solar cooling

An experimental investigation of an air-cooled diffusion absorption machine operating with a binary light hydrocarbon mixture (C₄H₁₀/C₉H₂₀) as working fluids and helium as pressure equalizing inert gas is presented in this paper. The machine, made of copper an available and very good heat conducting metal, is intended to be solar powered heat from flat plate or common evacuated tube collectors. The cooling capacity is 40–47 W respectively for 9 and 11°C chilled water temperature. Cold is produced at temperatures between −10 and +10 °C for a driving temperature in the range of 120–150 °C.     

Thermal and economical analysis of a central solar heating system with underground seasonal storage in Turkey

Thermal performance and economic feasibility of two types of central solar heating system with seasonal storage under four climatically different Turkey locations are investigated. The effects of storage volume and collector area on the thermal performance and cost are studied for three load sizes. The simulation model of the system consisting of flat plate solar collectors, a heat pump, under ground storage tank and heating load based on a finite element analysis and finite element code ANSYS™ is chosen as a convenient tool. In this study, the lowest solar fraction value for Trabzon (41°N) and the highest solar fraction value for Adana (37°N) are obtained. Based on the economic analysis, the payback period of system is found to be about 25–35 years for Turkey.     

Experimental study of vertical ground-source heat pump performance evaluation for cold climate in Turkey

Heat pump systems are recognized to be outstanding heating, cooling and water heating systems. They provide high levels of comfort as well as offering significant reductions in electrical energy use. In addition, they have very low levels of maintenance requirements and are environmentally attractive. The purpose of this study is to evaluate the experimentally performance and energy analysis of vertical ground-source heat pump (GSHP) for winter climatic condition of Erzurum, Turkey. For this aim, an experimental analysis was performed on GSHP system made up in the Energy Laboratory in the campus of Ataturk University. The experimental apparatus consisted of a ground heat exchanger, the depth of which was 53 m, a liquid-to-liquid vapor compression heat pump, water circulating pumps and other measurement and control equipments. Tests were performed under laboratory conditions for space heating, in which experimental results were obtained during January–May within the heating season of 2007. The experimentally obtained results were used to calculate the heat pump coefficient of performance (COP) and the system performance (COPs). The COP and COPs were found to be in the range of 2.43–3.55 and 2.07–3.04, respectively. This study also shows that the system proposed could be used for residential heating in the province of Erzurum which is one of the coldest climate region of Turkey.     

Novel composite sorbent for resorption systems and for chemisorption air conditioners driven by low generation temperature

The utilization of a composite sorbent (NaBr and expanded graphite) in chemisorption air conditioning systems driven by low-grade heat source, and in resorption systems with simultaneous heating and cooling effects was experimentally investigated using bench-scale prototypes. The mass of ammonia desorbed and adsorbed was measured, and used to calculate the specific cooling capacity. The sorbent produced 219 kJ kg⁻¹ of cooling at 5 °C and 510 kJ kg⁻¹ at 15 °C, when the heat source temperature was 65 °C and the heat sink temperature was 30 °C. The air conditioning system mean specific cooling power (SCP), and mean coefficient of performance (COP) were calculated based on the desorbed and adsorbed masses, and on the variation of temperature in the reactors. For the same heat source and heat sink temperatures mentioned above, the air conditioning system had a SCP of 129 ± 7 W kg⁻¹ and a COP of 0.46 ± 0.01, when cooling occurred at 15 °C. Regarding the utilization of the composite sorbent in resorption machines, the prototype was tested for production of cooling/heating at −5/50 °C, and at 10/70 °C. In the former condition, the COP was only 0.02, but in the latter condition, there was a tenfold increase in the COP, and the combined coefficient of performance and amplification reached 1.11, which indicates the energy saving potential of resorption systems using the studied sorbent.     

Performance assessment of HCFC-22 window air conditioner retrofitted with R-407C

This paper presents the experimental performance analysis of a 1.5 TR window air-conditioner, retrofitted with R-407C, as a substitute to HCFC-22. Experimental results showed that R-407C, for the operating conditions covered in this study, had lower cooling capacity in the range 2.1–7.9% with respect to HCFC-22. The coefficient of performance for R-407C was lower in the range 7.9–13.5%. The power consumption of the unit with R-407C was higher in the range 6–7% than HCFC-22. The discharge pressures for R-407C were higher in the range 11–13% than HCFC-22.This paper also presents simulation results of heat exchangers of an HCFC-22 window air conditioner retrofitted with R-407C. The simulation has been carried out using EVAP-COND, a heat exchanger model developed by National Institute of Standards and Technology, U.S.A. The simulated evaporator capacities are within ±3% of the experimentally measured cooling capacities for both refrigerants. Simulation results for R-407C and HCFC-22 are compared. The exit temperatures of R-407C are lower by 1.9 °C to 5.2 °C in the condenser and are higher by 3.2 °C to 3.8 °C in the evaporator than HCFC-22. Evaporating pressures of R-407C are higher by 4.5–5.3% as compared to HCFC-22. The pressure drops of R-407C are lower in both the evaporator and the condenser as compared to HCFC-22. The outlet temperatures of air for HCFC-22 and R-407C in both heat exchangers are nearly the same.     

A solar ejector cooling system using refrigerant R134a in the Athens area

This paper describes the performance of an ejector cooling system driven by solar energy and R134a as working fluid. The system operating in conjunction with intermediate temperature solar collector in Athens, is predicted along the 5 months (May–September). The operation of the system and the related thermodynamics are simulated by suitable computer codes and the required local climatologically data are determined by statistical processing over a considerable number of years. It was fount that the COP of ejector cooling system varied from 0.035 to 0.199 when the operation conditions were: generator temperature (82–92 °C), condenser temperature (32–40 °C) and evaporator temperature (−10–0 °C). For solar cooling application the COP of overall system varied from 0.014 to 0.101 with the same operation conditions and total solar radiation (536–838 W/m²) in July.     

Crystallization as a limit to develop solar air-cooled LiBr–H2O absorption systems using low-grade heat

In the present work the use of low-temperature solar heat is studied to produce cooling at 5°C, using a double-stage LiBr–H₂O air-cooled absorption cycle. A solar plant, consisting of flat plate collectors feeding the generators of the absorption machine, has been modeled. Operating conditions of the double-stage absorption machine, integrated in the solar plant without crystallization problems for condensation temperatures up to 53°C, are obtained. Results show that about 80°C of generation temperature are required in the absorption machine when condensation temperature reach 50°C, obtaining a COP equal to 0.38 in the theoretical cycle.A comparative study respect to single-stage absorption cycles is performed. Efficiency gain of the double-stage solar absorption system, over the single-stage one, will increase with higher condensation temperatures and lower solar radiation values. Single-stage cycles cannot operate for condensation temperatures higher than 40°C using heat from flat plate collectors. For higher condensation temperatures (45°C) the generation temperatures required (105°C) are very high and crystallization occurs. Condensation temperatures able to use in double-stage cycles may be increased until 53°C using heat from flat plate collectors without reaching crystallization.     

Analysis on a hybrid desiccant air-conditioning system

Hybrid desiccant-assisted preconditioner and split cooling coil system, which combines the merits of moisture removal by desiccant and cooling coil for sensible heat removal, is a potential alternative to conventional vapor compression cooling systems. In this paper, experiments on a hybrid desiccant air-conditioning system, which is actually an integration of a rotary solid desiccant dehumidification and a vapor compression air-conditioning unit, had been carried out. It is found that, compared with the conventional VC (vapor compression) system, the hybrid desiccant cooling system economizes 37.5% electricity powers when the process air temperature and relative humidity are maintained at 30 °C, and 55% respectively. The reason why the hybrid desiccant cooling system features better performance relative to the VC system lies in the improvement brought about in the performance of the evaporator in VC unit due to desiccant dehumidification. A thermodynamic model of the hybrid desiccant system with R-22 as the refrigerant has been developed and the impact of operating parameters on the sensible heat ratio of the evaporator and the electric power saving rate has been analyzed. It is found that a majority of evaporators can operate in the dry condition even if the regeneration temperature is lower (i.e. 80 °C).     

Performance testing and evaluation of solid absorption solar cooling unit

Based on solid-vapour intermittent absorption system, DORNIER a German Firm designed and fabricated a solar cooling unit, which utilizes thermal energy supplied by heat pipe vacuum tube solar collectors through thermosyphonic flow of water. The unit of 1.5 kWh/day cooling capacity uses ammonia as a refrigerant and IMPEX material as absorbent and does not have any moving part requiring no auxiliary energy. The IMPEX material (80% SrCl₂ and 20% Graphite) has high heat and mass transfer coefficient as well as high absorption capacity. Detailed experiments were performed on a unit in Delhi under real field conditions followed by theoretical analysis. Theoretical maximum overall COP of the unit is 0.143, and it depends upon the climatic conditions. Under field conditions, it was found that if the maximum daytime ambient temperature was 30°C and night time temperature 20°C, it took three sunny days to freeze water in the cooling box. After the second day, the temperature inside the cooling box remained 1°C. The overall COP was found to be 0.081 only. The automatic control valve based on mechanical/thermal principles however has defects and the problem of corrosion of the sealings needs to be solved. In climates where day time temperatures are high (Delhi summer 43°C–47°C during the day, 30°C–35°C during the night) and solar radiation relatively low (4–5 kWh/m²d) because of pollution and sand in the atmosphere, it is most unlikely that pressure in the ammonia circuit can reach values at which ammonia vapours start to condense. The unit, needs to be redesigned for such conditions.     

Experimental study of horizontal ground source heat pump performance for mild climate in Turkey

The aim of this study is to evaluate the performance of horizontal GSHP by considering various system parameters for winter climatic condition of Bursa, Turkey. For this purpose, a previously used experimental facility on cooling cycle [Coskun S, Pulat E, Unlu K, Yamankaradeniz R. Experimental performance investigation of a horizontal ground source compression refrigeration machine. International Journal of Energy Research 2008; 32: 44–56] was modified for the heating cycle. Soil thermal conductivity estimation was expanded and discussed. Preliminary numerical temperature distribution around GHE pipes was obtained. Tests were performed under laboratory conditions for space heating from December 2004 to March 2005. Variations of entering and leaving antifreeze solution temperatures, extracted heat from ground and rejected heat to the test room, super heat rate in evaporator and subcooling rate in condenser, total power consumption and coefficient of performance (COP) values for both the entire system and only heat pump unit (HPU) were obtained. Effect of outdoor temperature on system capacities and COP values with respect to outdoor air and mean soil temperatures were also presented. The COP of the entire system and HPU lie between 2.46–2.58 and 4.03–4.18, respectively. GSHP system was compared to conventional heating methods in the economical analysis and it was shown that the GSHP system is more cost effective than the all other conventional heating systems.     

Design and performance simulation of a new solar continuous solid adsorption refrigeration and heating hybrid system

In this paper, the design of a new continuous solid adsorption refrigeration and heating hybrid system driven by solar energy was proposed, and its performance simulation and analysis were made under the normal working conditions. Some performance parameters of the system were obtained, and the effects of water mass in water tank on the system's COP_cooling, COP_heating etc. were discussed. The simulation indicated: the system could refrigerate continuously with such a design, and at the conditions of that the daily sun-radiation is 21.6 MJ, the mean ambient temperature is 29.9°C, the evaporating temperature is 5°C, the heat-collecting coefficient of upper bed η is 60%, and the heat-transfer coefficient between lower bed and ambient α is 2 W/m² K, by day a hybrid system of single combined bed could furnish 30 kg hot water of 47.8°C, and had a mean COP_cooling of 0.18, a mean COP_heating of 0.34, a continuous mean SCP_a of 17.6 W/kg, a continuous mean SCP_c of 87.8 W/m², and a continuous mean SHP_c of 165.9 W/m²; and at night it had a cooling capacity of 0.26 MJ/kg of adsorbent, and a cooling capacity of 1.3 MJ/m² of heat-collecting area.     

Design and operation of an air-conditioning system fueled by wood pellets

A room-cooling system of 2 kW capacity fueled by wood pellets was designed, built and tested. The system was demonstrated during summer at the Yakushima Field Station of Kagoshima University, Japan. It contained a pellet feeder, a pellet burner, a heat exchanger, a lithium bromide–water absorption heat pump and a control unit. The volume of the test room was 36.9 m³ and ambient temperature 30 °C. The airflow temperature from the room unit was decreased to 16 °C by the system, and the room temperature could be successfully controlled to 24 °C steady state. Room heating in winter was also demonstrated. Since the air was heat exchanged, the overall energy efficiency of the cooling system was low at about 19%. However, the calculation based on the heat flow showed that the efficiency could be enhanced to about 75% by direct heating of the regenerator by the flue gas.     

Forecasting based on neural network approach of solar potential in Turkey

As Turkey lies near the sunny belt between 36 and 42°N latitudes, most of the locations in Turkey receive abundant solar energy. Average annual temperature is 18–20 °C on the south coast, falls down to 14–16 °C on the west coast, and fluctuates 4–18 °C in the central parts. The yearly average solar radiation is 3.6 kW h/m² day, and the total yearly radiation period is 2610 h. The main focus of this study is put forward to solar energy potential in Turkey using artificial neural networks (ANNs). Scaled conjugate gradient (SCG), Pola-Ribiere conjugate gradient (CGP), and Levenberg–Marquardt (LM) learning algorithms and logistic sigmoid transfer function were used in the network. In order to train the neural network, meteorological data for last 4 years (2000–2003) from 12 cities (Çanakkale, Kars, Hakkari, Sakarya, Erzurum, Zonguldak, Balıkesir, Artvin, Çorum, Konya, Siirt, Tekirdağ) spread over Turkey were used as training (nine stations) and testing (three stations) data. Meteorological and geographical data (latitude, longitude, altitude, month, mean sunshine duration, and mean temperature) is used as input to the network. Solar radiation is the output. The maximum mean absolute percentage error was found to be less than 6.78% and R² values to be about 99.7768% for the testing stations. These values were found to be 5.283 and 99.897% for the training stations. The trained and tested ANN models show greater accuracy for evaluating solar resource posibilities in regions where a network of monitoring stations have not been established in Turkey. The predictions from ANN models could enable scientists to locate and design solar energy systems in Turkey and determine the best solar technology.     

An experimental investigation into a solar assisted desiccant-evaporative air-conditioning system

In this experimental investigation a solar assisted open adsorption cooling system has been designed and tested under the local weather conditions of Basrah, Iraq. Data were obtained from June to September, inclusive, 1984. Tests were carried out hourly with a directly supply of hot air from a corrugated absorber solar air heater for regeneration. Also, tests were conducted at a constant regeneration temperature of 70°C using auxiliary heat. Adsorption was carried out by a rotary disk of silica gel. Three mass flow rates of process air were employed without recirculation. The performance of the solar air heater was obtained for both seasons, and the instantaneous efficiency was evaluated experimentally and analytically with results compared. Daily and seasonal coefficients of performance were obtained for the cooling system for the mass flow rates employed. A maximum seasonal average value of 2.8 was obtained for a mass flow rate of 0.075 kg/s. The system performance improved with higher regeneration temperature, higher process air mass flow rate and dry weather. It was possible to generate a cool supply of air at satisfactory conditions using solar energy only for all clear days under the local weather conditions.