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Thermal design and analysis of heat exchangers are predominantly conducted considering constant heat transfer coefficients. However, these vary along the length and affect the calculations of heat transfer rates and area allocations. The current paper investigates the variations in the heat transfer coefficients in plate heat exchangers (PHX), using different numerical approaches. The heat transfer coefficient is calculated at the inlet, outlet, and systematically selected intermediate points for each method. The analysis is conducted for two different systems, i.e., a laboratory-scale and an industrial scale PHX at different chevron angles. It is concluded that the effect of the variable heat transfer coefficient is more significant for the large-scale heat exchanger due to high flow rates, geometrical specifications, Reynolds number, and thermophysical properties. The deviation of the local heat transfer coefficient along the heat exchanger length is approximately 9–14% and 3–6% for industrial and laboratory scale PHX, while an area deviation of around 15% is observed. [ABSTRACT FROM AUTHOR]

Despite the wide applications of multi-effect vapor absorption systems, their energy requirement is relatively higher. Also, their exergy analyses found in the literature reveal that the exergy destruction rate at the absorber is quite significant and has the potential for improvement in its energy efficiency. In this work, the exergy destruction rate at the absorber is minimized using the penalty factor method against the optimized generator temperature of the double-effect vapor absorption system by considering absorber, evaporator, and condenser temperatures into consideration. Modeling of the double-effect vapor absorption system was performed using a thermodynamic toolbox in SIMULINK. The present model employed a refrigerant heat exchanger to enhance the system cooling capacity. The liquid-vapor ejector valve at the absorber also improved the mixing of the solution and refrigerant vapor resulting in lower irreversibility of the system. Results show that the coefficient of a performance increase by 2.4% with refrigerant heat exchanger and exergy loss at absorber decrease by 9.4% with ejector. The optimum performance was seen at the condenser and evaporator temperatures of 308.8 K and 278.1 K, respectively with an 8.2% improvement in exergetic efficiency. Finally, it is concluded that the multi-effect absorption system shows better performance by minimizing the irreversibility. [ABSTRACT FROM AUTHOR]

Shell-and-tube heat exchangers are frequently used in several industrial applications. A model was developed using engineering equations solver software to predict the performance of various baffle configurations of shell-and-tube heat exchangers. The model is based on the Bell-Delaware method for the segmental baffle, while mathematical correlations for the helical baffle are provided for design and analysis purpose. The accuracy of the present model is validated against the experimental data available in the literature. The results showed that helical baffles offer much higher performance compared to the segmental baffled heat exchanger. It was found that the performance of the helical baffle increases with increasing baffle angle until it reaches an optimum value; it then starts to decrease at an angle of 42°. [ABSTRACT FROM AUTHOR]

Concentric tube heat exchangers are widely used as lube oil coolers in large internal combustion engines. They are particularly preferred because of simple manufacturing, lower area, and better heat transfer characteristics. With the growing use of unconventional fuel-based lubricants, their design is continuously improved to achieve the required heat transfer characteristics. One of the emerging alternative oil is Tire Pyrolysis Oil (TPO) to minimize tire waste and achieve the waste-to-energy objective. The TPO is employed not only as diesel blended fuel but also as a lube oil because of its satisfactory tribological properties. The present work provides a detailed design and analysis of a concentric-tube micro-fin-based lube oil cooler for TPO applications. The design encompasses the thermal, hydraulic, and economic characteristics of the heat exchanger subjected to TPO, Ethylene Glycol (EG), and Crude Oil (CO). To achieve this a robust numerical model is developed and implemented using engineering equation solver software. The model is validated with experimental data first. Then a detailed parametric analysis is done to investigate the heat exchanger performance. It was observed that TPO offered a better heat transfer coefficient along with lesser power input and cost compared to EG and CO. For instance, in the case of a mass flow rate 0.1 kg/s, the heat transfer per unit pressure drop is highest for TPO with 5.86 m/sK followed by CO with 5.12 m/sK and EG with 0.3876 m/sK. Similarly, the annual operational cost is calculated as 27.7 k$, 31.4 k$, and ∼ 80.8 k$ for the TPO, CO, EG which shows the superiority of TPO as lube oil for engine applications. Based on thermal, hydraulic design and economic analysis, it is concluded that tire pyrolysis oil (TPO) is used in the concentric tube micro fin heat exchanger for applications of oil cooling. [ABSTRACT FROM AUTHOR]

Pakistan is among the countries that have already crossed the water scarcity line, and the situation is worsened due to the recent pandemic. This is because the major budget of the country is shifted to primary healthcare activities from other development projects that included water treatment and transportation infrastructure. Consequently, water-borne diseases have increased drastically in the past few months. Therefore, there is a dire need to address this issue on a priority basis to ameliorate the worsening situation. One possible solution is to shift the focus/load from mega-projects that require a plethora of resources, money, and time to small domestic-scale systems for water treatment. For this purpose, domestic-scale solar stills are designed, fabricated, and tested in one of the harshest climatic condition areas of Pakistan, Rahim Yar Khan. A comprehensive overview of the regional climatology, including wind speed, solar potential, and ambient temperature is presented for the whole year. The analysis shows that the proposed system can adequately resolve the drinking water problems of deprived areas of Pakistan. The average water productivity of 1.5 L/d/m2 is achieved with a total investment of PKR 3000 (<$20). This real site testing data will serve as a guideline for similar system design in other arid areas globally. [ABSTRACT FROM AUTHOR]