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In this study, the effects of fin design, fin material, and free and forced convection on junction temperature in automotive headlamp cooling applications of LED lights are researched by using ANSYS CFX 14 software. Furthermore a new methodology is presented for defining the optimum cylindrical fin structure within the given limits. For measuring the performance of methodology, analyses are carried out for various ambient temperatures (25 degrees C, 50 degrees C and 80 degrees C) and different LED power dissipations (0.5 W, 0.75 W, 1 W and 1.25 W). Then, analyses are repeated at different heat transfer coefficients and different fin materials in order to calculate LED junction temperature in order to see if the fin structure proposed by the methodology is appropriate for staying below the given safety temperature limit. As a result, the suggested method has always proposed proper fin structures with optimum characteristics for given LED designs. As another result, for safe junction temperature ranges, it is seen that for all LED power dissipations, adding aluminum or copper plate behind the printed circuit board at low ambient temperatures is sufficient. Also, as the ambient temperature increases, especially in high powered LED lights, addition of aluminum is not sufficient and fin usage becomes essential. High heat transfer coefficient and using copper fin affect the junction temperature positively. Magneti Marelli SpA

A re-circulating heat pump dryer (HPD) system was designed, constructed and tested at steady state and transient conditions. Refrigerant 134a was used as a refrigerant in this system. The tests were performed to observe behavior of HPD system. So, changes of temperature and relative humidity of drying air through the dryer and heat pump operating temperatures were observed during the drying process and effects of bypass air ratio (BAR) on the system?s parameters as system performance and specific moisture extracted ratio (SMER) at steady state were investigated. The HPD system was also tested to investigate temperatures and relative humidity changes of drying air during drying process on the system?s parameters depend on time. Air flow rate circulated through the HPD system was 554m3/h during the all tests. According to test results, the system?s parameters did not change up to 40% of BAR. Then the COP and SMER values were decreased after 40% of BAR. While SMER values changed between 1.2 and 1.4, COPsys changed between 2.8 and 3.3 depend on BAR. As well as during the drying process, the COP and SMER values were also affected and decreased depend on time.

Bu çalışmada, jeotermal enerji destekli, NH3-H 20 eriyiği ile çalışan tek kademeli absorbsiyonlu soğutma sisteminin, farklı eriyik konsantrasyonları ve tasarım parametrelerine göre optimizasyonu yapılmıştır. Parametrik değerlendirme sonrasında 3660 farklı tasarım oluşturulmuş ve bu tasarımlar çerçevesinde sistem performanslarının; ısıtıcı, buharlaştıncı, yoğuşturucu ve absorber sıcaklıkları ile değişimi enerji ve ekserji analiz metotları kullanılarak incelenmiştir. Hesaplamalarda NH3-H 20 eriyiğinin karışım oranları % 46 NH3-% 54 FLO, % 40 NH3-% 60 H20 , % 30 NH3-% 70 H20 , % 20 NH3-% 80 H20 şeklinde dikkate alınmıştır. Çalışmanın ayrıca; Simav jeotermal kaynakları kullanılarak tasarlanan ve optimize edilen absorbsiyonlu soğutma sisteminin faydalı ömrü 20 yıl olarak dikkate alınmış olup, bölgede ve yakın çevresinde yetişen üzüm, elma ve ayva gibi ürünlerin soğuk muhafaza yöntemi ile saklanması planlanarak, sistemin optimizasyonu Net Bugünkü Değer (NBD) metoduyla yapılan ekonomik değerlendirme sonucu belirlenmiştir. Optimum sistem için, STK değeri 0,5722 ve ekserji verimi 0,6201 olarak hesap edilmiş, ürün grubunun ayva olması durumunda, sistemin NBD'si 3.912.757,74 TL, elma olması durumunda 13.922.203.39 TL ve üzüm olması durumunda ise 59.803.554.33 TL olarak hesap edilmiştir. Elde edilen bu sonuçlar dikkate alındığında, Simav jeotermal kaynaklarının kullanıldığı absorbsiyonlu bir soğutma sisteminin yatırıma uygun olduğunu tespit edilmiştir. In this study, the single stage geothermal energy assisted absorption refrigeration system, working with ammonia-water solution, was optimized in the view of different solution concentrations and design parameters. Depending on parametric evaluation, a number of 3360 designs were made. In these frameworks, changes of the system performance by the effect of generator, evaporator, condenser and absorber temperature were investigated. The capacities of generator, evaporator, condenser, absorber, heat exchanger, pump, coefficient of performance (COP) and exergy efficiency were calculated by energy and exergy analysis. In the calculations, different ratios of NH3-H2O solution were taken into account as 46% NH3 - 54% H2O, 40% NH3 - 60% H2O, 30% NH3 - 70% H2O, 20% NH3 - 80% H2O. In further, an economical evaluation based on net present value analysis (NPV) was made for each design. In this purpose, the economic life of the system was taken as 20 years and the refrigerated products were chosen as grape, apple and quince taking the regional situations into consideration. The optimum design was determined using the results of NPV analysis. For the optimum design, COP of the system was determined as 0,5722 while the exergy efficiency was calculated as 0,6201. In this conditions, NPV values were calculated as 3.912.757,74 TL, 13.922.203,39 TL and 59.803.554,33 TL for the products of quince, apple and grape, respectively. According to these results, it was found that absorption refrigeration system assisted by Simav geothermal resources was respectable for investment.

This paper deals with an investigation of the effect and optimization of control parameters on the system performance in waste heat recovery application using mechanical heat pump (MHP). The experimental studies have been conducted under varying compressor speed, wastewater temperature and flow rate. The experiments have been planned based on Taguchi's L27 orthogonal array with each trial performed under different conditions of compressor's speed, wastewater temperature and flow rate. The optimum parameter combination has been obtained by using the analysis of signal-to-noise (S/N) ratio. The level of importance of the control parameters on the system performance has been determined by using analysis of variance (ANOVA). Main effects plots and interaction effects plots have been utilized to optimize and analyze the relation between the control parameters and the system performance. The results obtained from Taguchi method were also compared with ANN results. The experimental study indicated that it is possible to increase system performance significantly in the waste heat recovery application using MHP.

This paper relates to thermodynamic performance assessment of a geothermal district heating system (GDHS) using advanced exergetic analysis to identify the interactions among system components and the potential for improvement. It is introduced four new exergetic parameters, namely the exergetic fuel depletion ratio, the exergetic productivity lack ratio, the exergetic rehabilitation ratio, and the exergetic improvement potential for a GDHS. This analysis and new exergetic parameters are applied to the Bursa GDHS in Turkey. The results show that the advanced exergetic analysis is a more meaningful and effective tool than the conventional one for the system performance evaluation. The exergetic efficiencies for the conventional and advanced ones are 25.24% and 26.34%, respectively. The highest priorities for improvement of system components are in descending order of importance: the heat exchangers and the pumps for the conventional analysis, and only the heat exchangers for the advanced analysis. New exergetic parameters appear to be key indicators to show how much the system is improvable and apparently sustainable. The ratios of these parameters in the order given above are respectively 4.19%, 16.60%, 33.23% and 4.19%, for the Bursa GDHS. The heat exchangers have the highest values of exergetic rehabilitation ratio. Thus, there are improvement priorities of the heat exchangers. Bursa Jeotermal Enerji

It is important to provide a regular unidirectional air distribution in an operating room to reduce the number of particles. Measurements were taken in the one of the operating rooms at Uludag University Medical School, with laminar air flow unit and two-cornered outlet which was thought to have some airflow problems. Moreover, a three-dimensional computational fluid dynamics model has been developed where the measurements were taken in. The distributions of air velocity, temperature, and relative humidity have been examined and compared with the measurements to validate the computational fluid dynamics analyses. In addition to present model, four-cornered outlet operating room has been analyzed and compared with the results of two-cornered one. It is concluded that the case of four-cornered outlet provides more suitable thermal distribution, which results in a reduction of the particle numbers in the interior. Although there is no significant change in temperature and relative humidity in the operating room, air distribution changes dramatically.

This study examines experimentally the cooling application of a solar absorption system with interior energy storage that uses two different auxiliary systems. The experiments were performed at Uludag University, Bursa, Turkey on the 3rd and 4th of August 2010 that had the approximately same average outdoor temperature, 31°C. A solar hot water was delivered via a 40 m2 array of flat plate solar collectors that drove a lithium chloride (LiCl) absorption heat pump with a cooling power peak of 20 kW. A solar-powered air conditioning system was designed for heating and cooling in a test room that had a total floor space of 30 m2. Chilled water produced in the evaporator was supplied to the fan coil units, and the heat of condensation and absorption was rejected by means of a wet cooling tower. An electric heater and an air source heat pump were used as auxiliary systems for the absorption cooling application for two different cases when the solar energy was insufficient. Temperature variations were recorded for the absorption machine components, the test room, and the outdoors. The cooling energy, thermal energy, and daily average coefficient of performance (COP) of the absorption system were calculated for two days. Solar absorption cooling was considered for two different auxiliary systems and is presented in this manuscript. The results showed that the daily average COP of the absorption system was 0.283 for Case 1 and 0.282 for Case 2. For both cases, the interior energy storage of the absorption system enabled it to satisfy the cooling demand during the night while solar energy was not available.

This study presents a literature review, especially in recent years, on the absorption refrigeration systems (ARSs), the currently used refrigerant-absorbent pairs and their alternatives. Additionally, in this study, the thermodynamic analysis of ARS using commonly encountered solution pairs in the literature was carried out, and a user-friendly software package including visual components was developed. The effects of operating temperatures, the effectivenesses of solution, refrigerant and solution-refrigerant heat exchangers (SHE, RHE, SRHE), and selection of working fluid pair on the system performance were examined by using the developed package. It was concluded that performances of the cycles improve with increasing generator and evaporator temperatures, but reduce with increasing condenser and absorber temperatures. The performance of system was affected from the SHE more than the RHE and SRHE. While the use of SHE improves the system COP up to 66%, RHE and SRHE have an effect of only 14% and 6%, respectively. For that reason, the SRHE may not be considered practically significant. Suitable solutions depending on operating conditions showed variations with respect to generator and evaporator temperatures.

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.