In this study, the development of rinnenkarren systems is analyzed. During the field studies, 36 rinnenkarren systems were investigated. The width and depth were measured at every 10 cm on the main channels and then shape was calculated to these places (the quotient of channel width and depth). Water flow was performed on artificial rinnenkarren system. A relation was looked for between the density of tributary channels and the average shape of the main channel, between the distance of tributary channels from each other and the shape of a given place of the main channel. The density and total length of the tributary channels on the lower and upper sections of the main channels being narrow at their lower end (11 pieces) and being wide at their lower end (10 pieces) of the rinnenkarren systems were calculated as well as their average proportional distance from the lower end of the main channel. The number of channel hollows was determined on the lower and upper sections of these main channels. It can be stated that the average shape of the main channel calculated to its total length depends on the density of the tributary channels and on the distance of tributary channels from each other. The main channel shape is smaller if less water flows on the floor for a long time because of the small density of the tributary channels and the great distance between the tributary channels. In this case, the channel deepens, but it does not widen. The width of the main channel depends on the number and location of the rivulets developing on channel-free relief. The main channel becomes narrow towards its lower end if the tributary rivulets are denser and longer on the upper part of the main rivulet developing on the channel-free, plain terrain and their distance is larger compared to the lower end. The channel hollows develop mainly at those places where the later developing tributary channels are hanging above the floor of the main channel. Thus, the former ones are younger than the latter ones. It can be stated that the morphology of the main channels (shape, channel hollows, and width changes of the main channel) is determined by the tributary channels (their number, location and age).

Application of nanoparticles have been proven to aid heat transfer in engineering systems. This work experimentally investigated the performance of a domestic refrigerator under the influence of Al₂O₃ nanoparticles dispersed in mineral oil based lubricant at different charges (40, 60 and 80 g) of LPG refrigerant. The performance of the system was then investigated using test parameters including: power consumption, evaporator air temperature (pull-down time), to attain the specified International Standard Organisation (ISO) requirement for standard evaporator air temperature with small refrigerator size. Results showed improved pull down time and steady state evaporator air temperatures for the nano-lubricant based LPG. Improvement of about 11.79% in coefficient of performance (COP) was obtained with Al₂O₃-lubricant based LPG at 40g charge on the refrigerator system, while reduction of about 2.08% and 4.41% in COP were observed at 60 and 80 g charge of LPG based on Al₂O₃-lubricant respectively. Furthermore, reduction of about 13.4% and 19.53% in the power consumption of the system were observed at 40 and 60g charges of Al₂O₃-lubricant based LPG, whereas at 80 g, an increase of about 1.28% was recorded. Using Al₂O₃-LPG nano-refrigerant in domestic refrigerators is economical  and also a better alternative to pure LPG.

Global energy agencies and commissions report a sharp increase in energy demand based on commercial, industrial, and residential activities. At this point, we need energy-efficient and high-performance systems to maintain a sustainable environment. More than 30% of the generated electricity has been consumed by HVAC-R units, and heat exchangers are the main components affecting the overall performance. This study combines experimental measurements, numerical investigations, and ANN-aided optimization studies to determine the optimal operating conditions of an industrial shell and tube heat exchanger system. The cold/hot stream temperature level is varied between 10 ℃ and 50 ℃ during the experiments and numerical investigations. Furthermore, the flow rates are altered in a range of 50–500 L/h to investigate the thermal and hydraulic performance under laminar and turbulent regime conditions. The experimental and numerical results indicate that U-tube bundles dominantly affect the total pumping power; therefore, the energy consumption experienced at the cold side is about ten times greater the one at the hot side. Once the required data sets are gathered via the experiments and numerical investigations, ANN-aided stochastic optimization algorithms detected the C10H50 scenario as the optimal operating case when the cold and hot stream flow rates are at 100 L/h and 500 L/h, respectively.