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The transition to renewable energy is hindered by the level of acceptance in society. The role of education in schools is crucial, and while numerous studies have been conducted, there is still a lack of exploration into the depth of the materials. This research was carried out to assess the readability level of material on renewable energy from geothermal resources in Vocational High School textbooks. The descriptive quantitative method was used, conducted in 19 Vocational High School with a study program in Technology and Engineering in Surakarta. The sample size was 340 respondents. Data were collected from textbooks and questionnaire results. The Gunning Fog Index scores indicated the material had low readability level with scores of 20, 18, and 21 for texts 1, 2, and 3. Text 1 is taken from book titled 'Energy Conversion Machines', Text 2 from 'Sustainable Energy Saving through Building', and Text 3 from 'Basic Knowledge of Mechanical Engineering. Additionally, the responses of readers indicated that more than 50% of respondents could easily comprehend the content in texts 2 and 3. Resulting, for text 1, over 50% of respondents reported understanding the content with some difficulty. These three books are also commonly used, making this research a valuable recommendation for stakeholders in curriculum design and educational planning.

Biomass stands out as a promising availability source of sustainable carbon energy due to its low pollution profile and versatile applications. This study investigates the multistage catalytic gasification (MCG) of coconut shells, employing thermal and catalytic cracking processes in a two-step gasification approach. Local source catalysts, including dolomite, kaolin, and zeolite, were utilized as eco-friendly additives at temperatures ranging from 200 to 300 °C. Zeolite emerged as the most effective catalyst, producing the highest energy content at 6.21 MJ/kg. Conversely, kaolin resulted in higher CO2 emissions. A blend of zeolite and kaolin achieved the highest energy content at 5.43 MJ/kg. However, the combined use of catalysts showed negligible improvements compared to individual catalysts. The study demonstrates that multistage catalytic gasification enhances syngas production and reduces tar content during the gasification of coconut shells. Optimal pyrolysis temperatures were identified within the 500–600 °C range. In conclusion, the introduction of multiple stages in the catalytic cracking process ensures a stable breakdown of hydrocarbon chains, promoting the exposure of gasification products to lighter compounds. Multistage catalytic gasification enhances oxygen supply for oxidation, thereby improving syngas production while mitigating tar and ash content.

This study aimed to enhance the efficiency of the solar water heater (SWH) due to the increasing demand of renewable energy. It compared use three different solar collector models, namely Model A (square-shaped polycarbonate), Model B (v-corrugated zinc), and Model C (trapezoidal aluminium) to identify the most cost-effective configuration. The models were subjected to experiments in real operating conditions during the summer season in Indonesia. Various parameters, including solar radiation intensity, wind speed, inlet and outlet temperatures, and flow rate, were measured every 10 min from morning to afternoon. Additionally, the study employed a trickle and one-way flow rate system. The results showed that Model B achieved the highest total efficiency at 50%, followed by Models A and C at 47% and 34%, respectively. The 120 Lph flow rate exhibited better performance in absorbing useful heat energy than the 240 Lph flow rate. Based on these findings, all three models were recommended for the household-scale SWH applications. Model A showed the most promising economic value but had a shorter lifespan due to the tendency of polycarbonate to deform. In contrast, Model B and Model C, using zinc and aluminium, offered longer lifespans.

Artificial Intelligence is a technology that has rapidly developed in this decade. Its capability to perform tasks previously achievable only by humans has made this technology popular and utilized across various sectors, including vocational education. In vocational education, Artificial Intelligence plays a role in enhancing the efficiency and effectiveness of teaching. One example is the development of adaptive learning programs that can adjust the curriculum according to students' abilities and needs. Additionally, Artificial Intelligence is also used to evaluate student performance and provide automatic feedback. This system can assist in assessing and monitoring student performance, enabling teachers to focus on teaching and student development. This study used the Systematic Literature Review (SLR) method. This method is used to identify, assess, evaluate, and interpret all available research within the field of the relevant phenomenon, guided by specific research questions. By using this method, a systematic review and identification of journals can be conducted, following predefined steps. The data for this study is obtained from relevant journals between the years 2013 to 2021, totaling 15 literature journals from various countries. The primary goal of this research is to provide a deeper understanding of the role of this technology in vocational education and to present a framework that can be used as a guide for the implementation of Artificial Intelligence. It is anticipated that this research will assist educators and decision-makers in effectively utilizing Artificial Intelligence to enhance learning, skills, and vocational student preparation for the continually evolving job market.

The world's energy consumption shows an increasing trend. Unfortunately, it is still dominated by the use of fossil energy. This condition results in concerns that an energy crisis will occur due to running out of non-renewable energy and an environmental crisis of global warming. One of the technology sectors that consumes a lot of energy is computer servers and data centers. This technology sector is growing rapidly due to the increasingly complex computing and larger data. One of the main causes of inefficiency in this technology is a decrease in performance due to an increase in temperature. Therefore, effective and efficient technology is needed to overcome the increasing operating temperature of computer servers and data centers. One of the most prominent cooling technologies to solve this problem is immersion colling. This method has developed in various types with their respective advantages and disadvantages according to application needs. Therefore, review literature is needed to comprehensively discuss the development of immersion cooling technology from the past until now and projected developments in the future. In more detail, this paper comprehensively compiles the latest findings of immersion cooling technology which includes an overview of the cooling system, history, implementation, construction type, and advantages.

The outbreaks of infectious diseases that spread across countries have generally existed for centuries. An example is the occurrence of the COVID-19 pandemic in 2020, which led to the loss of lives and economic depreciation. One of the essential ways of handling the spread of viruses is the discovery and administration of vaccines. However, the major challenges of vaccination programs are associated with the vaccine cold chain management and cold storage facilities. This paper discusses how vaccine cold chain management and cold storage technology can address the challenges of vaccination programs. Specifically, it examines different systems for preserving vaccines in either liquid or frozen form to help ensure that they are not damaged during distribution from manufacturing facilities. Furthermore, A vaccine is likely to provide very low efficacy when it is not properly stored. According to preliminary studies, the inability to store vaccine properly is partly due to the incompetency of many stakeholders, especially in technical matters. The novelty of this study is to thoroughly explore cold storage technology for a faster and more comprehensive vaccine distribution hence it is expected to be one of the reference and inspiration for stakeholders.

Even though HOTS-based learning has been implemented since 2018, students' readiness has not been tested. This study aims to test the willingness of students to learn based on HOTS in Indonesia. Readiness is reviewed based on the 4C criteria: critical thinking, creative, communicative, and collaborative. This study uses a descriptive quantitative approach. The sample was selected by random cluster sampling of 2.645 Indonesian students. The test method uses a questionnaire and observation. Data were taken by using observation, interview, and questionnaire techniques. The results show that students look active during discussions but still find it challenging to develop their creativity to solve problems. In quizzes, students should start to get used to the thinking process at levels C4 to C6, but students still choose C1 to C3. This study concludes that students are ready for criteria C1 to C3 and unprepared for learning at levels C4 to C6. Students need intense coaching and mentoring to support the successful implementation of HOTS-based learning.

Vocational students are confronted by intricate demands once they graduate. Despite the considerable need for vocational graduates in the workforce, most students have a limited understanding of digital and vocational information. This study used a descriptive quantitative method to determine the influence of digital and vocational information literacy on students' learning outcomes in three vocational schools in the Sragen Regency. Cluster Random Sampling was used to select a sample of 111 students. Data on digital and vocational information literacy were collected using a questionnaire, while those on the learning outcomes were obtained from the student’s grades. The results showed that digital literacy influences vocational students’ learning outcomes with a significance of 0.000 0.05. Vocational information literacy influences the students’ learning outcomes with a significance of 0.000 0.05. Furthermore, digital and vocational information literacy simultaneously influence the students’ learning outcomes with a significance of 0.000 0.05. These results indicate the necessity to familiarize and increase the students’ literacy skills to improve learning outcomes. The results indicated that digital and vocational literacy partially and collectively influenced learning outcomes by 48.2%. Therefore, classroom instruction needs to be structured around learning models that actively stimulate the development of digital and vocational literacy skills, preparing students for workplace competitions. Consequently, teachers should consistently implement learning strategies that create a meaningful connection between the school environment and the realities of the professional world.

Solar water heaters (SWH) are a low-cost method for generating hot water for various purposes. Therefore, this research focuses on investigating a modified V-corrugated zinc collector combined with an aluminum foil foam insulator and a 5 mm thick plywood base at the bottom. The experiments were conducted under hot climate conditions in the Central Java region of Indonesia. The effect of flow rate, with 120, 180, and 240 Lph, was compared and analyzed using passive and open systems. Data was retrieved at 10-min intervals from 8:00 a.m. to 3:00 p.m. The results showed that the highest energy efficiency of 50% was achieved at a flow rate of 240 Lph, with 40% and 34% energy efficiency at flow rates of 180 Lph and 120 Lph, respectively. Additionally, the highest collector efficiency was 61%. These findings suggested that higher flow rates were more efficient in SWH with V-corrugated zinc collectors. Therefore, it was recommended to use V-corrugated collectors due to their low production cost and ability to produce 50% energy efficiency.

Among the two pyrolysis methods, the two-stage type gives better results than the single-stage in converting mixed municipal solid waste (MMSW) into synthetic oil (O-Synthec) and gaseous products (G-Synthec). However, the double energy supply for the heating process in the first and second reactors needs to be considered in terms of efficiency. Therefore to complete the research of two-stage pyrolysis, this study improvised a two-stage co-pyrolysis process supported by a Long Fixed-Bed Catalytic Insert (LFCi) attached to the inner wall of the reactor. In the test, 500 g of MMSW with 8 components was fed into a reactor with LFCi containing a dolomite natural catalyst. The co-pyrolysis process was carried out at a temperature variation of 400–550 °C, and the best results obtained were used as a reference for variations in reaction time from 120 to 210 min. Based on the physical and chemical properties, the co-pyrolysis O-synthec and G-synthec products were subjected to Gas Chromatography Mass Spectrometry (GCMS) analysis and American Society for Testing and Material (ASTM) standard to physical properties test. The results were compared with those of one-stage pyrolysis, direct catalytic and without catalyst. Based on the results, the presence of LFCi in the reactor had a significant effect in increasing the mass yield of O-Synthec at 550 °C with a residence time of 150 min. An increase of 20,14% and decrease 16.77% of O-Synthec and G-Synthec respectively were achieved compared to the uncatalyzed, although the presence of 15.5% peak area oxygenated fractions and 3.0% peak area acid needs to be considered as it impacts the calorific value. The dominant aromatic compound indicates that O-Synthec has similarities with conventional gasoline fuel. Meanwhile, the non-condensable gas (G-Synthec) produced contains a concentration of hydrocarbon compounds in the distribution of C1–C12, which is dominant with tripropylaluminum, formic acid and butenes. The high content of formic acid and tripropylaluminum compounds in G-Synthec must be considered because they are very corrosive and hazardous to the environment.

Online learning has increased rapidly in Indonesia's higher education since the government enforced to combat the spread of COVID-19. However, inequality in implementation has become an issue in several countries. In Indonesia, with archipelagic and mountainous topography has several challenges. Therefore, the present study is aimed to evaluate and analyze the benefits, challenges, and suggestions of online learning in Indonesia for future improvement. A total of 271 students were surveyed and provided complete information regarding the survey. Quantitatively, the instrument of the survey data is analyzed by using SPSS software. Qualitatively, data from open-ended participants' responses were analyzed by qualitative content analysis to explore the findings from the survey. The result showed that online learning was more efficient, provided easy communication, improve students' engagement, and developed their virtual learning skills. However, it was also found that the overall students were still unsatisfied since the uneven infrastructures of internet connectivity and learning arrangements not good enough. In line with this, media, processes, facilitators skills, and assessments needed further improvement. Students’ suggestions for improving online learning quality are discussed as well.

Waste Heat Recovery System (WHRS) technology, e.g., Organic Rankine Cycle (ORC) has been explored as a solution to the increase in geothermal potential, possibly applied in binary or combined form, as a single-flash plant. This approach utilizes waste brine obtained from the separator. The purpose of this study, therefore, was to determine the performance of R134a refrigerant on ORC systems, using scroll-expander. The experiment was conducted with motor different frequency, at 7.5 Hz, 10 Hz, 12.5 Hz, 15 Hz, 17.5 Hz, and 20 Hz, evaporator temperature regulation of 95 °C, condenser at 10 °C, and an initial working fluid pressure of 5 bar. The results showed modifications in the ORC system performance with scroll-expander, alongside the motor frequency, which influenced the net power and energy efficiency. In addition, the maximum speed produced by the expander was 505.8 rpm, while the highest for energy efficiency achieved from the system was 3.17%, at a motor frequency of 7.5 Hz, with a resulting net power of 584.5 Watt.

Several countries around the world currently use the conventional method to produce salt but this has been discovered to have some disadvantages such as dependence on rainfall, air humidity and temperature, land, sunlight, and wind speed. This, however, makes the production dependent on the season of a region such that a high rainfall leads to a decrease in production. Meanwhile, it is possible to produce salt by separating the particles from their water and creating a droplet forced by airflow and heat convection. Therefore, this research was conducted to examine a salt production process using the spraying and heating method which involves the application of a nozzle assisted by a blower and heater. The results showed the use of a nozzle and blower affected the salt production time and weight. The best yield and time were found at 0.1 mm nozzle with 1 h 50 min and 1067.67 g weight respectively while 4.9 m/s blower speed had 1026 g weight in 2 h 5 min. It is also important to note that the salt produced using this method is more white and smoother than using conventional methods.

The global increase in world population is followed with a rise in waste generation and energy needs in various sectors. Organic waste, also known as biomass, is the most substantial contribution of the waste generation and it also can be utilized in energy generation. Therefore, the purpose of this study is to analyze the syngas production from co-gasification using Renewable Densified Fuels (RDF) with gasification temperature, lower heating and gas emission values, on the performance of the biomass co-gasification process in an open-top downdraft fixed bed gasifier. In this study organic waste used woods, coconut fibers and rice husks in pellets to blend the compositions of raw materials during the co-gasification process. The method used is the co-gasification technique with feed pellets WCF (wood-coconut fiber) and RH (rice husk) in various compositions, for example: 100% WCF, with 0% of RH, 75 WCF: 25 RH, 50 WCF: 50RH, 25 WCF: 75RH and all 100% RH with 0WCF. Furthermore, the syngas testing was directly measured on the burner with TCD type Shimadzu 8A gas chromatography. The result showed that the highest reactor temperature in the pyrolysis zone is 700 °C–900 °C which was significantly stable at 800 °C with oxidation temperature of 1000 °C–1100 °C. Furthermore, the result of the synthetic gas showed that the highest lower heating value of 100% WCF pellet composition at 3.582 kJ/Nm3 and lower heating value of RDF blending composition (75:25) at 3.392 kJ/Nm3. The increase in pellet fuels also leads to a rise in the LHV syngas value. These results produced a visually low tar content and ash particles in all compositions by approximately 30–35% of the initial mass, with the lowest ash in 100% WCF pellets composition at 0.25 g.

The Raque Hilsch Vortex Tube (RHVT) is a heat pump system that uses the phenomenon of compressed vortex airflow in a tube for cooling and heating. This study aims to determine the effect of pressure and fraction on RHVT by cooling the surface of the hot tube naturally and forcefully. Tube type testing was conducted with a pressure variation of 0.5–1.5 bar and a fraction of 30%–70%. The results of the analysis show that forced cooling on the surface of the hot tube decreases the heating performance (Th, ΔTh, Q˙h, ηish, and COPh) and improves the cooling performance (Tc, ΔTc, Q˙c, ηisc and COPref). The higher pressure increases the performance of Th ΔTh, Q˙h, Tc ΔTc, and Q˙c, and decrease the performance of ηish, COPh, ηisc, and COPref. The fraction 40% is the most optimal parameter for the performance of Tc ΔTc, Q˙c. The 60% fraction works best for Th, ΔTh, Q˙h, ηish, and COPh, while the fraction 70% works best for Q˙c and COPref. The most optimal performance values include Th (41 °C), ΔTh (14 °C), Q˙h (2.369kJ/s), ηish(24.21%), COPh (0.092), Tc (13.450 °C), ΔTc (13.550 °C), Q˙c (3.280kJ/s), ηisc (20.84%), and COPref (0.123).

Data centers have become one of the most important elements of the Industrial Revolution 4.0. However, conventional data centers face the problem of electricity consumption, with 40% being used for the cooling systems. This led to the proposed development of immersion cooling as one of the methods to solve the current data center cooling system issues. This paper, therefore, was aimed at determining the factors affecting the immersion cooling performance using mineral oil. The experiment was further conducted by creating an immersion cooling box and running the server by loading the software. The contribution and effect of each factor were also determined through the use of the Taguchi Method with Orthogonal Array L8. The performances measured include the CPU temperature and Energy Consumption using the effect of the inlet-outlet location, flowrate and cooling fan speed as the Taguchi factors. The results showed that the CPU temperature was affected by cooling fans with 71.278% and energy consumption by 75.034%.

Promoting electricity supply in remote areas and islands by developing power plants using organic waste biomass fuel, is a strategic effort in increasing energy supply. This study aimed at investigating the characteristic of gasification toward air fuel ratio variation, especially the temperature, lower heating value and tar content on the gasification performance with multi integrated gas cleaner systems (IGCS) used as producer gas purification unit. The plant was built with downdraft gasifier and multy IGCS which includes cyclones, rectangular venturi scrubbers, and rotary separators. The experimental investigation were carried out with air fuel ratio parameters at 0.48, 0.5, 0.54, scrubbing water discharge at 1.26, 2.62, 3.33 l/min, and 0.9 rotary separator using a suction speed of 3.4, 4.4 m/s. All parameters were intended to produce clean gas with high heating value, low tar and impurities. The experimental results showed air fuel ratio 0.54 produced the largest gas at lower heating value of 8500 kJ/Nm3, however the tar content is relatively high at 3788.1 mg/ m3. The installation of multi IGCS reduced the tar to 210.45 mg/ m3 with water discharge of 3.33 l/min and 4.4 m/s suction speed. Therefore, the electrical power generated was 100 W.

The performance of the vortex tube is low compared to a conventional heat pump engine based on Freon refrigerants, and therefore, there is a need for an experiment on how to improve its efficiency. This data article aims to analyze the effect of the new vortex tube design on cold temperature (Tc), hot temperature (Th), delta cold temperature (ΔTc), delta hot temperature (ΔTh), heat transferred as cooling effect (Q˙c), heat transferred as heating effect (Q˙h), isentropic efficiency as cooling effect (ηisc), isentropic efficiency as heating effect (ηisc), the coefficient of performance refrigeration (COPref), and coefficient of performance heat pump (COPh), which is tested based on pressure and fraction variations. The data were obtained from the experimental measurements. Data were collected at conditions with temperature controlled at 27 ± 0.1°C. All measuring instruments were supposed to be consistent for at least 5 min for data to be collected, although retrieval was conducted 4 times.

This experiment uses the Municipal Solid Waste (MSW) from households and traditional markets as feed materials in the Integrated Downdraft Gasifier and Multi Integrated Gas Cleaner System (IGCS). The IGCS consist of cyclone, rectangular venturi scrubber, and rotary separator. The data from the experiment show the gasification characteristics such as temperature, Low Heating Value (LHV) and tar content. The parameter consists of Air Fuel ration (AFR) at 0.48, 0.5, 0.54 scrubbing water discharge at 1.26, 2.62, 3.33 l/min, and 0.9 rotary separator using suction speed at 0.9, 3.4, 4.4 m/s, respectively. The data also show the power output of the plant and energy balance of the system. This data can be used as reference for the further development of Integrated Downdraft Gasifier and Multi-Integrated Gas Cleaner systems.

Indonesia has the potential of saving from 10% to 30% of energy in the commercial sector which consists of trade, hotels, restaurants, finances, government agencies, schools, hospitals, and communications. By simultaneously serving as building envelope material and power generator, BIPV systems can represent savings in the cost of materials and electricity. It reduce the use of fossil fuels and emission of ozone depleting gases, and also add architectural interest to buildings. However, the temperature rise poses a challenge for BIPV, given that it manifests itself in electrical efficiency and overheating. The experiments present in this study aim at understanding the behavior of the PV-PCM systems in realistic outdoor uncontrolled conditions to determine how effective they are. In addition, the PV-PCM systems were tried in the low latitude and hot climate of Banda Aceh, Indonesia. Experiments were conducted outdoors at the Engineering Faculty in Syiah Kuala University, located in Banda Aceh, Indonesia (05:57 N, 95.37 E). In this study, both paraffin wax and beeswax were used as a phase change material. The final results showed that the electrical efficiency of PV panels without PCM is ranged between 6.1% and 6.5%. While for PV panels with PCM the efficiency is ranged at 7.0–7.8%. This proved that the process of water cooling is capable of increasing the efficiency of PV panels. Keywords: PV, Phase change material, Temperature, Efficiency

This research aims to evaluate the performance of a fluidized bed boiler in an ethanol production plant through exergy and irreversibility analysis. The study also includes the optimization of the pre-heater and the deaerator in order to improve the system efficiency. Operational data from the ethanol production plant was collected between 2015 and early 2016. The total exergy derived from the fuel was determined to be 7783 kJ/s, while the exergy efficiency of the system was found to be 26.19%, with 2214 kJ/s used in steam production, while 71.55% was lost to component irreversibility and waste heat from the pre-heater. The exergy efficiencies of individual components of the system such as the boiler, deaerator, and pre-heater were found to be 25.82%, 40.13%, and 2.617%, respectively, with the pre-heater having the lowest efficiency. Thus, the pre-heater has the highest potential to significantly improve the efficiency of the boiler system. The optimization of the pre-heater shows that a rise in temperature in the outlet of the pre-heater positively affects the exergy efficiency of the deaerator.

In this paper thermal and hydraulic optimization of water to water chevron type plate heat exchanger is presented. The optimization is performed using the multi objective genetic algorithm in MATLAB optimization environment. Constrain matrix is a set of different geometrical parameters of plate heat exchanger within the logical bounds. The two objective functions are pressure drop of hot side and heat transfer. Due to conflicting nature of these objective functions, no single solution can satisfy both of the objective function simultaneously. The increase in heat transfer will results in increase in pressure drop, therefore, optimization results are presented as Pareto Front. Multi objective genetic algorithm tool was employed to find a set of optimum solution which was trade-off between pressure drop and heat transfer. At the end, sensitivity analysis was performed to analyse the effect of geometrical parameters of heat exchanger on thermal and hydraulic performance. The sensitivity results show that the heat transfer and pressure drop are greatly affected by the vertical port centre distance, plate spacing and number of thermal plates.

The objectives of this study are to perform the exergy analysis and ambient temperature optimization of the Kamojang geothermal power plant by employing Engineering Equation Solver (EES). The geothermal capacity is 55 MW and the field is vapor-dominated reservoir with temperature 245 °C. In the initial state temperature, pressure and mass flow data are collected from the plant operation. The study results show that system has overall efficiency of 35.86% which means that only 111,138.92 kW electrical power can be extracted from 309,000 kW thermal power being produced by 10 production wells of Kamojang. This low efficiency is due to irreversibility associated with different processes and components in the system. The largest irreversibility occurs in condenser due to which 53% of total energy is disposed into the environment. Ambient temperature at Kamojang varies from 17 to 20 °C. The effect of this variation in temperature is also investigated and it is observed that higher temperature does not have any significant impact on system efficiency.

Municipal solid waste (MSW), disposed of at open dumping sites, poses health risks, contaminates surface water, and releases greenhouse gasses such as methane. However, pyrolysis offers the opportunity to convert MSW into Bio-Oil (BO) for clean energy resource. In this paper, an MSW sample consisting of plastic, paper and cardboard, rubber and textiles, and vegetable waste is pyrolysed on a laboratory scale in a fixed-bed vacuum reactor. In the non-isothermal process, the sample was fed into the reactor and then heated. In the isothermal process, the reactor is first heated and then the sample is added. The non-isothermal process created greater BO in both quality and quantity. The BO had a larger amount of gasoline species than diesel-48 fuel, with at 33.44%the BO produced by isothermal pyrolysis and 36.42% in non-isothermal pyrolysis. However the product of isothermal pyrolysis had a higher acid content that reduced its heating value.

The objective of this research is to investigate the reduction in fuel consumption and emission in spark ignition engine using blended bioethanol-gasoline and novel radiator-tube heater. Different percentages of ethanol – 0, 5, 10, 15, 20, 25 and 30% – are employed. The blended fuel is then pre-heated by sending it into a tube-heater-installed upper tank radiator which has different shape. The results show a significant reduction in fuel consumption and emission in engine. The best economical fuel consumption occurs in the tube-heater with a fin pipe of 10 mm space at 2.153 × 10−3 cc per cycle or 5.632%. However, the most economical fuel consumption occurs when 25% of bioethanol is added to fuel at 3.175 × 10−3 per cycle. This decreases fuel consumption by 8.306%. The highest decrease in fuel consumption occurs when fuel blended with 25% of bioethanol and tube-heater of 10 mm 6.236 × 10−3 cc per cycle or 16.313% is combined. In terms of emission reduction, the tube-heater with a space of 20 mm between fins (Tube 20) using a fuel mixture of 25% ethanol and 75% gasoline produced the lowest CO emissions.

Calophyllum inophyllum are plants with a propensity of being used as raw materials in liquid fuel production, in an attempt to overcome energy and environmental crisis, due to the use of fossil fuels. However, high viscosity problem of calophyllum inophyllum seed oil has restricted its utilization in internal combustion engines. Therefore, this study was conducted to experimentally upgrade the physical and chemical properties of calophyllum inophyllum seed oil performed using a thermal-catalytic technique at three successive temperatures, which include 400 °C, 500 °C and 600 °C. A natural dolomite catalyst was activated at 500 °C for 2 h and then employed with the reaction time chosen according to the expected temperature. The results show the highest yields of liquid fuel obtained (42.33%), occurred at 500 °C. Meanwhile, gas Chromatography-Mass Spectroscopy (GC-MS) and ASTM standards presented the oil to be mainly composed of 29.43% aliphatic and 38.99% aromatic compounds. In addition, the viscosity of Calophyllum inophyllum seed oil at 40 °C had decreased from 52.48 cSt to 5.73 cSt, and based on GC-MS evaluation, it was seen to significantly contain a hydrocarbon range of C5–C20, and a small fraction greater than C20. The nature of pyhsics shows calophyllum inophyllum seed oil is product similar to conventional diesel fuel which strengthens the possibility of being used as a substitute. Finding of this study has never been carried out experiments with natural dolomite catalysts using two-stage pyrolysis (thermal-catalytic reactors). Keywords: Calophyllum inophyllum, Liquid fuel, Upgrading, Two-stage pyrolysis, Catalysts

The thermal efficiency of conventional solar air heaters could be significantly improved by making some design configurations. In this study, a solar chimney air heater was employed and the effect of glazing, fins and convection (natural/forced) on the thermal efficiency of the heater was investigated. It was found that the incorporation of glazing and fins improved the performance of the heater. Further, the heater showed improved efficiency when operated under forced convection mode. Among the designs, the forced induced glazed solar chimney air heater with fins displayed the highest average thermal efficiency of 16.50%. Keywords: Solar chimney air heater, Heater efficiency, Forced convection, Glazing, Fins

In this paper, a study of room air conditioning performance when using a liquid-suction heat exchanger retrofitted with R290 has been carried out with the aim of determining the influence of LSHX and R290 in terms of refrigeration effect, power consumption, COP, and heat exchanger effectiveness. A liquid-suction heat exchanger (LSHX) with length of 178 mm was designed and installed in air conditioning pipelines. The RAC used is a split-type with input power of 395 W and initial refrigerant R22. The experiment was conducted on two system conditions with 6 tests each. The results showed that LSHX provides an advantage in improving the energy efficiency of the standard RAC systems. Energy savings and increased COP can be as much as 27.69% and 38.29%. The adoption of R290 also helps reduce the potential of ozone depletion and global warming. It can be concluded that the combination of LSHX and R290 can produce better performance. Keywords: Room air conditioner, LSHX, R290