Orhan Büyükalaca

Analysis of variable-base heating and cooling degree-days for Turkey

The degree-day method is one of the well-known and the simplest methods used in the Heating, Ventilating and Air-Conditioning industry to estimate heating and cooling energy requirements. In this study, the heating and cooling degree-days for Turkey are determined by using long-term recent measured data. Five different base temperatures ranging from 14 to 22°C are chosen in the calculation of heating degree-days. In the case of cooling degree-days, 6 different base temperatures in the range 18 to 28°C are used. Yearly heating and cooling degree-days are given both in tabular form and as counter maps for all the provinces of Turkey (78 weather stations).

Optimum shape and dimensions of ducts for convective heat transfer in laminar flow at constant wall temperature

One knows that a certain geometry exists for a given pressure loss in a duct, where maximum heat transfer occurs. In this work, the maximum heat transfer and the optimum geometry for a given pressure loss have been calculated for forced convective heat transfer in different duct shapes for laminar flow conditions. Simple equations which enable calculation of these optimum values for all Pr numbers and for all shapes of duct cross-sectional areas have been derived.

New outdoor cooling design data for Turkey

In this study, new outdoor design conditions for space heating were determined for 78 locations within Turkey according to the format recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc. (ASHRAE). Dry-bulb temperature corresponding to 99%, 99.6% and 97.5% annual cumulative frequency of occurrence, the mean and standard deviation of the annual minimum dry-bulb temperatures were obtained. These calculations used hourly data measured during at least 13 years. The current heating design conditions used in the calculation of space heating load in Turkey were analyzed based on their frequency levels. Comparison of the existing space heating design data with the data obtained in this study revealed that the current space heating design temperatures are generally stringent and provide total protection.

Bin weather data for Turkey

One of the well-known and simple steady-state methods used to predict heating and cooling energy consumption of buildings is the bin method that requires reliable and detailed bin data. In this study, the bin data for Turkey are determined by using long-term measured data. The bin data for dry-bulb temperature from -36 °C to 45 °C with 3 °C increments are calculated in six daily 4-h shifts for 78 provinces of Turkey.

Detailed weather data for the provinces covered by the Southeastern Anatolia Project (GAP) of Turkey

The Southeastern Anatolia Project (GAP) of Turkey is a multi-faceted and integrated regional development project based on the concept of sustainable development. The project area covers nine provinces (AdIyaman, Batman, DiyarbakIr, Gaziantep, Kilis, Mardin, Siirt, SanlIurfa and SIrnak) in the Euphrates-Tigris basins and Upper Mesopotamia plains. In this study, detailed weather data are presented for these provinces (except SIrnak). The data consist of new outdoor design conditions for heating and cooling according to the format recommended by the American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc. (ASHRAE), the heating and cooling degree-days for different base temperatures and the bin data for dry-bulb temperatures from -21 °C to 45 °C with 3 °C increments, in six daily 4-h shifts. These data are determined by using long-term recently-measured data.

Design of Regenerative Heat Exchangers

Rotary regenerators are used widely for energy recovery, both in industrial and air-conditioning applications, because of the advantages they have over other types of heat exchangers. In this study, a mathematical model for the design of rotary regenerators is presented. The method is valid for all kinds of channel geometries that form the matrix of a rotary regenerator and can be used for all rotational speeds. The validity of the method is tested with the experimental and numerical results available for rotational speeds between 0.05 and 7 rev/min. A good agreement between the model and the experimental numerical results is obtained. The method presented can therefore be recommended for the safe design of rotary regenerators.

Generation of Typical Solar Radiation Year for Mediterranean Region of Turkey

Typical solar radiation data is very important for the calculations concerning many solar applications. In this study, typical solar radiation years for six provinces located in the Mediterranean region of Turkey are generated from the daily global solar radiation data measured at least for 14 years, using the Finkelstein-Schafer statistical method. The typical daily global solar radiation data for the locations considered is presented throughout a year in a tabular form. The data obtained is also analyzed. It is expected that the typical data presented for the Mediterranean region, which is rich for solar energy potential in Turkey, will be useful to the designers of solar energy systems.

Development of an Artificial Neural Network Model for the Prediction of the Performance of a Silica-gel Desiccant Wheel

This work presents mathematical equations derived from Artificial Neural Networks (ANNs) for the estimation of dry bulb temperature and specific humidity at the outlet of a desiccant wheel to predict useful data for designers and engineers. The neural network model comprises five inputs and two output neurons that define the outlet conditions (dry bulb temperature and specific humidity) of a desiccant wheel. The results obtained by the ANN model are compared with the actual data by using input variables. The results show that the mean absolute percentage errors for dry bulb temperature and specific humidity are found to be 0.80% and 1.56% respectively; and the correlation coefficient (R) values obtained are approximately 0.986 for both output variables. The root mean square errors, which is another significant point in this study, are found to be 0.54% and 0.18% for dry bulb temperature and specific humidity respectively.

Experimental Investigation of Thermal Performance in a Tube With Detached Circular Ring Turbulators

This article deals with the experimental investigation of thermal performance of detached circular ring turbulators in turbulent flow regime. The experiments were conducted by four different circular rings. Two different pitch ratios (1 and 2) and two different distances (1 mm and 2 mm) at which the circular rings were detached from the tube wall were considered in the experiments. Uniform heat flux was applied to the external surface of the tube and Reynolds number was varied from 4350 to 24,920. The tube with circular ring turbulators introduced both higher heat transfer and higher pressure drop than the smooth tube, depending on pitch ratio and distance. According to the experimental results, the Nusselt number and friction factor increased with decreasing of pitch ratio and distance. Therefore, the circular ring turbulator with a pitch ratio of 1 and distance of 1 mm offered the highest heat transfer rate accompanied by the highest pressure drop. The highest thermal performance efficiency of 26% was also achieved for this case at a Reynolds number of 4421. Evidently, the experimental results revealed that the best operating regime of all circular ring turbulators was found at low Reynolds number, leading to a more compact heat exchanger.