Recent Research Trends in Genetic Algorithm Based Flexible Job Shop Scheduling Problems

Flexible Job Shop Scheduling Problem (FJSSP) is an extension of the classical Job Shop Scheduling Problem (JSSP). The FJSSP is known to be NP-hard problem with regard to optimization and it is very difficult to find reasonably accurate solutions of the problem instances in a rational time. Extensive research has been carried out in this area especially over the span of the last 20 years in which the hybrid approaches involving Genetic Algorithm (GA) have gained the most popularity. Keeping in view this aspect, this article presents a comprehensive literature review of the FJSSPs solved using the GA. The survey is further extended by the inclusion of the hybrid GA (hGA) techniques used in the solution of the problem. This review will give readers an insight into use of certain parameters in their future research along with future research directions

Model Development and Transient Seasonal Performance Analysis of a Solar Space Heating System under Climate Conditions of PAKISTAN

The model-based transient system simulation approach is very effective for a performance assessment of solar systems under various climate conditions. In the current study, a hybrid array of flat and evacuated tube collector was analyzed for space heating using a panel radiator for a room with a volume of 1600 ft3 at different flow rates. A detailed model is developed in TRNSYS that consists of a hybrid collector array, storage tank and pumping device along with a building load component. Using transient simulation, the performance of the hybrid solar space heating system was analyzed from December to February for the subtropical climate of Taxila, Pakistan. The results revealed that at flow rates of 350, 450 and 550 kg/h, the range of temperature gain of the hybrid collector array vary from 2.8to 15.4 °C, 1.7 to 11.6 °C and 1.2 to 9.2 °C from December to February, respectively, whereas the variation in efficiencies are 25.2 to 70.4%, 22 to 70.2% and 18.4 to 68.1% for December, January and February, respectively. In addition, it is observed that about 5.29 and 7.97% better seasonal efficiency is achieved for flow rate 350 kg/h as compared to 450 and 550 kg/h. The resulted room temperature varies from 22.3 to 26.8 °C, 22.2 to 27 °C and 22.4 °C to 30 °C for December, January and February to ensure desired thermal comfort. Overall, the results show that solar heating systems are viable to achieve the thermal comfort in winter and thus can significantly reduce gas consumption in the country

Experimental development, techno-economic and environmental analysis of a hybrid solar space heating system in a subtropical climate

Conventional modes of space heating are expensive and cause greenhouse gas emissions resulting in global warming. In this paper, an experimental analysis of a hybrid solar space heating system consisting of flat plate collectors (FPC) and evacuated tube collectors (ETC) along with a convective radiator is presented. Techno-economic and environmental analysis of the system is performed under real winter conditions in a subtropical climate. The experimental setup is designed such that flat plate collectors and evacuated tube collectors can also be operated separately for comparative analysis with the hybrid system (HC). The experimental results show that ETC achieved a maximum average energy efficiency of 72 % followed by the hybrid collector (HC) and FPC with energy efficiencies of 61 % and 57 %, respectively. The maximum exergy efficiency for ETC, HC and FPC are 54 %, 42 % and 33 % respectively in the month of December with low ambient temperatures. The corresponding maximum sustainability index achieved by ETC, HC and FPC, is 1.76, 1.52 and 1.39 respectively. In addition, the panel radiator achieved a maximum heat gain of 1484 W with an average room temperature in the range of 16.4–24.3 ℃. The economic analysis shows that the benefit-to-cost ratio for the hybrid varies from 0.82 to 1.6 and the payback period varies from 8.9 to 7.41 years compared to the electric heater for an inflation rate of 6–13 %. About 38 % more life cycle cost is observed for electric heater as compared to HSSHS. Environmental analysis reveals that 99 % and 78 % more greenhouse gas emissions are caused by conventional heaters compared to hybrid systems. Thus, a hybrid arrangement of FPC and ETC can be more beneficial for space heating compared to individual installations of these low-temperature solar collectors

Small-Sized Parabolic Trough Collector System for Solar Dehumidification Application: Design, Development, and Potential Assessment

The current study presents a numerical and real-time performance analysis of a parabolic trough collector (PTC) system designed for solar air-conditioning applications. Initially, a thermodynamic model of PTC is developed using engineering equation solver (EES) having a capacity of around 3 kW. Then, an experimental PTC system setup is established with a concentration ratio of 9.93 using evacuated tube receivers. The experimental study is conducted under the climate of Taxila, Pakistan in accordance with ASHRAE 93-1986 standard. Furthermore, PTC system is integrated with a solid desiccant dehumidifier (SDD) to study the effect of various operating parameters such as direct solar radiation and inlet fluid temperature and its impact on dehumidification share. The experimental maximum temperature gain is around 5.2°C, with the peak efficiency of 62% on a sunny day. Similarly, maximum thermal energy gain on sunny and cloudy days is 3.07 kW and 2.33 kW, respectively. Afterwards, same comprehensive EES model of PTC with some modifications is used for annual transient analysis in TRNSYS for five different climates of Pakistan. Quetta revealed peak solar insolation of 656 W/m2 and peak thermal energy 1139 MJ with 46% efficiency. The comparison shows good agreement between simulated and experimental results with root mean square error of around 9%