Air-Conditioning Engineers Research Articles

Experimental investigation of thermophysical properties of ethylene glycol based secondary fluids

Aqueous solutions of ethylene glycol are commonly used as secondary fluids in different indirect refrigeration systems and heat pumps as well as nanofluids. A very extensive literature review has been done, including more than 90 references published from 1905 to 2023. Despite the wide application and importance, especially in the energy sector, ethylene glycol solutions seem to be less investigated in low temperature ranges and more research is required to improve the quality and quantity of available data. The novelty of this paper is to investigate the most important thermophysical properties of ethylene glycol solutions in low temperatures. In this study a different approach was made and solutions having a specific freezing point temperature (between -5 and -50 ºC) rather than specific concentration were investigates in temperature ranges applicable for different cooling applications. The concentrations giving a certain freezing point temperature seemed to deviate in some cases with 1–2 wt-% between different sources. Nevertheless, the density results were in rather good agreement with all reference data. The viscosity results were lower by up to ±10% compared to reference values. Additionally, the obtained experimental results for thermal conductivity were higher by up to 12% compared to ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) data. The specific heat capacity results were higher by up to 14.6% and 5.4% than current reference data. There is a high probability that the current ASHRAE data for specific heat are actually indirectly calculated values from thermal conductivity data and not validated using differential scanning calorimetry techniques.

Optimalisasi Ventilasi Ruang Kelas untuk Mencegah Penularan Covid-19 dengan Setting Experiment

The spread of the SARS-CoV-2 virus has forced many schools to implement health protocols such as wearing masks, social distancing, and limiting the number of students in classrooms when face-to-face learning resumes as it did before the pandemic. This is due to the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) stating that Covid-19 can spread through the air (airborne). In addition to implementing health protocols, another important thing is to maintain classroom ventilation. By increasing the ventilation of outside air into the classroom, the risk of virus transmission can be reduced, and the indoor air quality can be improved. Introducing as much outside air as possible into the room is one important way to prevent the spread of Covid-19 because it can reduce the concentration of the virus in the room. ASHRAE (American Society of Heating, Refrigerating, and Air Conditioning Engineers) recommends a minimum of 6 ACH (Air Change per Hour) for classrooms. Research conducted on one middle school classroom in Tangerang Selatan, equipped with 2 AC units and 1 window, showed that the ASHRAE standard can be met by opening the window at least 50% during learning activities and turning on 1 AC unit with the fan setting at full speed to achieve an ACH greater than 6. If besides wanting to prevent the transmission of Covid-19, you also want to create comfort during the learning process, you can turn on both AC units with the fan setting at low to full speed. Keywords: Airborne, ASHRAE, Social distancing, US-CDC, WHO

설비공학 분야별 최근 연구 동향: 2022년 설비공학논문집 발표논문에 대한 종합적 고찰

This article provides an overview of the papers published in Korean Journal of Air-Conditioning and Refrigeration Engineering (KJACR) in 2022. The following is a summary of papers reviewed.BR (1) Papers published in the KJACR encompass a wide range of topics, including energy consumption analysis, indoor environment evaluation, building energy-saving techniques, ventilation systems, renewable energy systems, and economic analysis of mechanical facilities.BR (2) The research topics in the field of indoor thermal environment and IAQ (Indoor Air Quality) included ventilation, air cleaning, cooling/heating load calculations, renewable energy applications, carbon emission reduction, and assesment of building energy performance, among other related subjects.BR (3) In the field of refrigeration, researchers have the topics for the evaluation of thermal properties of refrigerants like R448A and R449A, studying the correlation between heat pump expansion valve performance and flow, designing variable speed scroll compressors, predicting the performance of adsorption heat exchangers, and characterizing compression chillers, among other relevant investigations.BR (4) Papers published in the field of heat and heat transfer included the studies on fuel cells, analysis of heat transfer mechanisms, efficiency evaluation of industrial heat exchangers, examining thermal conductivity and viscosity of carbon dioxide mixtures, investigating the thermal runaway phenomenon in lithium-ion batteries, and analyzing the efficiencies of interstitial thermal storage district heating systems.

Occupancy and Thermal Preference-Based HVAC Control Strategy Using Multisensor Network

Human-in-the-loop Heating, Ventilation and Air Conditioning (HVAC) control-based methodologies have gained much attention due to continual discomfort compliance of occupants in residential and commercial buildings; spawning thermal comfort research interest in leveraging emerging advanced technologies to address the prolonged problem of discomfort and energy efficiency. In the past, thermal comfort studies have been conducted to determine the thermal sensation, preference and comfort based on the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Global Thermal Comfort Database II and customized dataset through machine learning. The ASHRAE Database II is an open-source database that includes sets of objective indoor climatic observations with corresponding subjective evaluations by the building occupants who were used as subjects in experiments. Environmental parameters and occupants’ skin temperature have been used to develop machine learning algorithms to predict thermal comfort indices in both indoor and outdoor settings. However, none of these studies have investigated merging environmental parameters and thermal images to predict thermal comfort indices of occupants. In this study, the holistic understanding of individuals thermal comfort environment was considered by fusing analog environmental sensors and thermal images captured at the time of the subjective measurement. Wavelet scattering features were obtained from the occupants’ thermal image surroundings and joined to the environmental parameters. This research developed different machine learning models, processing methods and evaluated the results based on the fused dataset. The results show the possibility of real time prediction of occupancy and thermal preference through classical machine learning, and stacked models with high accuracy. The proposed framework achieved an estimated 45% mean energy savings during a ten-day energy analysis.

Simulation-based assessment of ASHRAE Guideline 36, considering energy performance, indoor air quality, and control stability

This study assesses American Society of Heating, Refrigerating and Air-Conditioning Engineers Guideline 36 (G36) with a typical medium office building. Specifically, this study employed a Modelica model of a variable air volume (VAV) system that serves this building, which includes components for representing indoor virus transmission and filtration. It then implemented the G36 control sequences for both water-side and air-side equipment in Python. After that, this study conducted the assessment by co-simulating G36 and the Modelica model using the Building Operations Testing Framework. Unlike existing works, this work has three unique features: (1) It considers the interactions between control sequences for water-side and air-side equipment of the studied VAV system. (2) It assesses the performance of G36 from the perspective of IAQ. (3) It examines the short-term behaviors of the studied building under G36 to understand the control stability. This assessment confirms significant energy savings from G36, largely because of the interaction between supply air temperature and hot water controls. It also reveals a trade-off between the ability to slow the spread of virus and the energy performance via demand controlled ventilation. Lastly, it emphasizes the necessity of tuning local feedback control when implementing G36.

Two-stage multi-step energy model calibration of the cooling systems of a large-space commercial building

Buildings play a major role in energy expenditure, representing 40% of Europe’s total energy consumption. It is estimated that heating, ventilation, and air conditioning systems consume between 50–60% of the total energy spent inside the building, thus corresponding to 20% of global worldwide energy consumption. Hence, there is a need to improve the accuracy of building thermal simulation and energy models that are essential in regulatory compliance calculations. In the present study, the authors empirically validate an optimization-based calibration methodology based on its application to a fully operational commercial building located in Pamplona, Navarre. The methodology used a white-box two-stage model in EnergyPlus, which combines a load profile object and a district cooling component to distribute the cooling load inside the building’s thermal zones. The study optimized the parameters and performance curves of different cooling system components using a second-generation non-sorting genetic algorithm in jEPlus software and 985 h of ten-minute time-step data. Finally, a multi-level benchmark is executed, which evaluates the electric energy consumption of the building’s heat pumps and the interior temperature of the different thermal zones for summer 2020 conditions. The assessment of the thermal and energy performance of the simulation model was conducted according to the requirements of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Guideline 14-2002, and the Chartered Institution of Building Services Engineers, Operation Performance Technical Memoranda 63.

Evaluation of thermal environment and human thermal comfort in 8 types of public places from 2019 to 2021

Objective: To evaluate the thermal environment of different types of public places and the thermal comfort of employees, so as to provide scientific basis for the establishment of microclimate standards and health supervision requirements. Methods: From June 2019 to December 2021, 50 public places (178 times) of 8 categories in Wuxi were selected, including hotels, swimming pools (gymnasiums), bathing places, shopping malls (supermarkets), barber shops, beauty shops, waiting rooms (bus station) and gyms. In summer and winter, microclimate indicators such as temperature and wind speed were measured in all kinds of places, combined with the work attire and physical activity of employees in the places. Fanger thermal comfort equation and center for the built environment (CBE) thermal comfort calculation tool were used to evaluate the predicted mean vote (PMV), predicted percent dissatisfied (PPD) and standard effective temperature (SET) according to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 55-2020. The modification effects of seasonal and temperature control conditions on thermal comfort were analyzed. The consistency of GB 37488-2019 "Hygienic Indicators and Limits in Public Places" and ASHRAE 55-2020 evaluation results on thermal environment was compared. Results: The thermal sensation of hotel, barber shop staff and the gym front-desk staff were moderate, while the thermal sensation of swimming place lifeguard, bathing place cleaning staff and gym trainer were slightly warm in summer and winter. Waiting room (bus station) cleaning and working staff, shopping mall staff felt slightly warm in summer and moderate in winter. Service staff in bathing places felt slightly warm in winter, while staff in beauty salons felt slightly cool in winter. The thermal comfort compliance of hotel cleaning staff and shopping mall staff in summer was lower than that in winter (χ(2)=7.01, 7.22, P=0.008, 0.007). The thermal comfort compliance of shopping mall staff in the condition of air conditioning off was higher than that in the condition of air conditioning on (χ(2)=7.01, P=0.008). The SET values of front-desk staff in hotels with different health supervision levels were significantly different (F=3.30, P=0.024). The PPD value and SET value of the front-desk staff, and the PPD value of cleaning staff of hotels above three stars were lower than those of hotels below three stars (P<0.05). The thermal comfort compliance of front-desk staff and cleaning staff in hotels above three stars was higher than that in hotels below three stars (χ(2)=8.33, 8.09, P=0.016, 0.018). The consistency of the two criteria was highest among waiting room (bus station) staff (100.0%, 1/1) and lowest among gym front-desk staff (0%, 0/2) and waiting room (bus station) cleaning staff (0%, 0/1) . Conclusion: There are different degrees of thermal discomfort in different seasons, under the condition of air conditioning and health supervision, and the microclimate indicators can not fully reflect the thermal comfort of human body. The health supervision of microclimate should be strengthened, the applicability of health standard limit value should be evaluated in many aspects, and the thermal comfort of occupational group should be improved.

Uncertainty method and sensitivity analysis for assessment of energy consumption of underground metro station

An accurate calculation of energy consumption is a precondition for energy underground metro station design, which determines the amount of energy geostructure. This study develops a simplified deterministic method for the underground metro station energy performance that accounts for weather and interior heat gain uncertainty. A Monte Carlo technique with Latin hypercube sampling is then employed to confirm the probability distributions of the peak load, average yearly load and annual energy demand, and compared to deterministic method to improve the design robustness. The sensitivities of 14 input variables with respect to the underground metro station energy performance are discussed through three sensitivity methods. The simplified deterministic method is more accurate than the DeST and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) in describing the fluctuation of the underground metro station energy performance. The uncertainty distribution of energy performance is advantageous to the system design, considering both safety and economy. Moreover, a comparison with the deterministic method is performed to determine the reasonability of the safety factor 1.2, which is usually used in practical programs. The peak load is dominated by outdoor parameters, while there are no control parameters for the average yearly load or annual energy demand.

An experimental study on the determination of a hermetic reciprocating compressor’s discharge and suction losses

The most popular approach to determine compressor losses is to generate compressor pressure-volume indication diagrams. The pressure-volume indication diagram of a novel hermetic reciprocating compressor for household refrigerators operating with R600a was experimentally obtained under American Society of Heating, Refrigerating and Air-Conditioning Engineers (54.4°C/−23.3°C) and additional specific working conditions of (40°C/−25°C), (25°C/−20°C) and (35°C/−15°C). Apart from most studies, experiments have been performed using a calorimeter. The alteration of suction and discharge pressures with crank angle of the investigated compressor was presented as both graphical and numerical information during condensation and evaporation, separately. As a result of the analyses, total compressor losses increased with decreasing the condensation pressure. These losses were 10%, 8.7%, 5.7% and 4.6% of the total work and they were observed at the same speed of 1300 rotation per minute (rpm) as the lowest one under all operating conditions. Besides, the suction line losses having the largest losses in the compressor were calculated as 50.1%, 50.9%, 64.9% and 67.9% of the total one, and it has been determined that they increased with increasing the condensation pressure. Due to the more complex design of the equipment in the suction line, the losses in this region were found to be higher than those in the discharge line, as expected.

Modelling an air handling unit, building and occupant variation regarding energy, moisture and frost protection based on measurements of an air handling unit and occupants’ moisture supply

Objectives of this paper are to propose a reasonable simulation model that can handle condensation and frost formation in heat exchangers dependent on moisture concentration and outdoor climate conditions, and to analyze risk of frost formation and discuss different frost protection strategies. Using psychometrics, American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) heat exchanger calculation, condensation and frost calculation methods, simulations models for heat recovery ventilation and energy recovery ventilation are developed. It is concluded that the risk of frost in heat exchangers is higher in northern Sweden than in southern Sweden and Denmark due to low outdoor air temperatures during the winter, however heat recovery systems in Copenhagen and Gothenburg still has a risk of frost formation even though these cities has relatively warm weather conditions. Out of several simulation models that are created during the study, the detailed model that takes condensation effect into consideration, is proven to be worthy to be used in further investigations, due to results that more accurately represent real word conditions. Risk of frost formation becomes significantly lower in every city when heat recovery ventilation is changed into energy recovery ventilation. Even though heat recovery ventilation is simulated only with the simplified model, it is safe to assume that it will still be effective in reality. Although bypass strategies were effective at eliminating the risk of frost in heat recovery units, they are not as efficient from an energy perspective. The more air is by-passed through the cross-flow plate heat exchanger, the fewer opportunities there are to recover energy from exhaust air, which leads to lower supply air temperatures and higher energy need for heating a living space.

Development of Conventional Refrigeration Control System Learning Media, Automatically Cooling and Defrost System

Development of Learning Media aims to design a Conventional Automatic Refrigeration Control System Design for Refrigeration and Defrosting Systems so that it can assist the learning process in Class XI Refrigeration Engineering. This research is a type of R&amp;D level 3. This study used a questionnaire as an instrument to collect data from content experts, media experts, and students. The results of the material expert trial obtained a percentage value of 93.33%, with very decent qualifications, the media expert trial results obtained a percentage of 97.64%, with very decent qualifications, the small group trial results obtained a percentage value of 90.25% , with very decent qualifications, the results of the large group trial data obtained a percentage of 90.04%, qualifications Based on the research results, the media is feasible and good to be used as a learning medium in the subject of Refrigeration Systems and Installation in class XI TP majoring in Electrical Engineering, package refrigeration and air conditioning engineering expertise at SMK Negeri 1 Denpasar

Comparative Study of the Impact of Bio-Sourced and Recycled Insulation Materials on Energy Efficiency in Office Buildings in Burkina Faso

This research presents a comparative study of different bio-sourced and recycled insulation materials and their impact on energy consumption of office buildings located in Ouagadougou, a city with a dry hot climate. A thorough assessment of the country’s meteorological and urban development data from 2004 to 2018 was conducted for climatic data. EnergyPlus was used for thermal comfort based on the American Society of Heating, Refrigerating, and Air-conditioning Engineers Standard (ASHRAE) 55 adaptive comfort model and energy analysis by calculating and comparing the yearly energy consumption, heat transfer through the building envelope, and discomfort degree hours. A four-story “H”-shaped office building made of cement blocks with a fixed north–south orientation and a 30% window-to-wall ratio served as the base case for this study to perform two rounds of multiple simulations and evaluate the most effective insulation material. First, exterior walls were insulated, and then the roof and inner floors were insulated using the best material from the first round. The findings confirmed hemp wool as the best performing bio-sourced insulation material, which reduces by 25.8% and 17.7% the annual cooling energy demand at 114,495 kWh and the annual energy consumption at 203,598 kWh, respectively, contributing to saving up to 43,852 kWh in annual energy consumption. Hemp wool impacted wall, roof, and internal floor heat transfer by reducing them by 90.86% at 12,583 kWh, 85.1% at 6666 kWh, and 88.1% at −2664 kWh, respectively, while the discomfort degree hours were reduced by 17.6% at 9720.12. The outcomes provide patterns, explanations, and inferences that may be generalized to other projects in Burkina Faso, especially, and sub-Saharan African countries, in general, where most buildings are not well insulated. The availability of these bio-based and recycled insulation materials may also serve as proof to foster a circular economy in the Burkina Faso construction industry.

CFD Investigation of Ventilation Strategies to Remove Contaminants from a Hospital Room

The primary requirement in designing air conditioning systems in healthcare facilities is eliminating contaminants. It is considered one of the crucial health elements in building design, particularly in the presence of many airborne diseases such as COVID-19. The purpose of this numerical research is to simulate various ventilation designs for a hospital room model by taking into account results obtained by previous researchers. Four designs with three airflows, 9, 12, and 15 ACH (Air Change per Hour), are applied to explore the capacity of the ventilation system to remove contaminants. The objective is to determine the influence of airflow and the diffuser location distribution on the pollutants elimination represented by carbon dioxide. The Reynold Averaged Navier–Stokes (RANS) equations and the k-ε turbulence model were used as the underlying mathematical model for the airflow. In addition, boundary conditions were extracted from ASHRAE (American Society of Heating, Refrigeration, and Air-Conditioning Engineers Society) ventilation publications and relevant literature. Contrary to what was expected, this study’s results demonstrated that increased ventilation alone does not always improve air distribution or remove more contaminants. In addition, pollutant removal was significantly affected by the outlet’s location.

Optimization of a Solar Chimney with a Horizontal Absorber for Building Ventilation: A Case Study

A study is conducted to optimize the geometry of a solar chimney equipped with a horizontal absorber in order to improve its performances in relation to the provision of ventilation. The problem is tackled through numerical solution of the governing equations for mass, momentum and energy in their complete three-dimensional and unsteady formulation. The numerical framework also includes a turbulence model (k-ε) and a radiant heat transfer (DO) model. Moreover, a Multi-Objective Genetic Algorithm (MOGA) is employed to derive the optimal configuration of the considered solar chimney. It is shown that an air velocity of 0.2 m/s can be obtained. This value is the minimum allowed air velocity according to the ASHRAE’s (American Society of Heating, Refrigerating and Air-Conditioning Engineers) adaptive comfort approach.

Quantifying Energy Reduction and Thermal Comfort for a Residential Building Ventilated with a Window-Windcatcher: A Case Study

Previous studies on window-windcatchers have shown their effectiveness in capturing the prevailing wind and redirecting it into a building, increasing the actual-to-required ventilation ratio by 9%, above what is required by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). However, the effect of implementing the proposed system on energy performance, energy costs, and thermal comfort has not been studied. Therefore, here, we investigate and test the implementation of the window-windcatcher on a typical residential building, using a validated DesignBuilder model. Compared to the base case (no window-windcatcher), the total annual energy consumption of the entire building (Etot,b), and consequently the cost, is reduced by approximately 23.3% (i.e., from 18,143 kWh/year to 13,911 kWh/year) when using the window-windcatcher. The total annual reduction in thermal discomfort hours is estimated to be 290 h, which corresponds to an average monthly reduction of approximately 24 h.

Facilities Development with Training of Instructors in Maintenance and Display Case Repair in the Work Training Center (BLK) of Kuningan District

The Kuningan West Java Vocational Training Center (BLK) is ready to create manpower to fill the world of work or independent businesses, to reduce unemployment rates. The condition of work training centers that have new buildings but are not yet supported with adequate equipment and human resources and according to needs still require support from stakeholders to improve their quality. Bandung State Polytechnic, especially the Department of Refrigeration and Air Conditioning Engineering, is experienced enough and feels the need to contribute to the development program of the BLK Kuningan, especially in the field of Facilities Development and Instructor Training in the Field of Maintenance and Repair of Display Cases at BLK Kuningan Regency. This program aims to increase the role of the BLK in increasing the competence of Human Resources according to the needs of the labor market. The method implemented is through the Facility Development and Instructor Training Program in the Field of Maintenance and Repair of Display Cases. This activity has been carried out in theory and practice with a ratio of 20% theory and 80% practice in the field which was held at BLK Kuningan. The outputs that have been achieved include training participants having sufficient competence as instructors in the field of refrigeration and air conditioning engineering, especially regarding maintenance and repair of display case machines, availability of job sheets and theory and practice modules on basic refrigeration, especially for display case machines, a set training unit display case and its service equipment.&#x0D;

Facilities Development with Training of Instructors in Maintenance and Display Case Repair in the Work Training Center (BLK) of Kuningan District

The Kuningan West Java Vocational Training Center (BLK) is ready to create manpower to fill the world of work or independent businesses, to reduce unemployment rates. The condition of work training centers that have new buildings but are not yet supported with adequate equipment and human resources and according to needs still require support from stakeholders to improve their quality. Bandung State Polytechnic, especially the Department of Refrigeration and Air Conditioning Engineering, is experienced enough and feels the need to contribute to the development program of the BLK Kuningan, especially in the field of Facilities Development and Instructor Training in the Field of Maintenance and Repair of Display Cases at BLK Kuningan Regency. This program aims to increase the role of the BLK in increasing the competence of Human Resources according to the needs of the labor market. The method implemented is through the Facility Development and Instructor Training Program in the Field of Maintenance and Repair of Display Cases. This activity has been carried out in theory and practice with a ratio of 20% theory and 80% practice in the field which was held at BLK Kuningan. The outputs that have been achieved include training participants having sufficient competence as instructors in the field of refrigeration and air conditioning engineering, especially regarding maintenance and repair of display case machines, availability of job sheets and theory and practice modules on basic refrigeration, especially for display case machines, a set training unit display case and its service equipment.&#x0D;

Application of a Model Based on Rough Set Theory (RST) to Estimate the Energy Efficiency of Public Buildings

The study was carried out on a group of 85 public buildings, which differed in type of use, construction technology and heating systems. From the collected data, a set of qualitative and quantitative variables characterizing them in terms of heat demand was extracted. In this paper, the authors undertook to test the suitability of a model based on rough set theory (RST), which allows the analysis of imprecise, general and uncertain data. To obtain input data for the RST model in quantitative form, the authors used an alternative approach, which is a method based on the thermal properties of buildings. The quality of the predictive model was evaluated based on the following indicators, such as the coefficient of determination (R2), the mean bias error (MBE), the coefficient of variance of the root mean square error (CV RMSE) and the mean absolute percentage error (MAPE), which are accepted as statistical calibration standards by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers). A quality-acceptable predictive model must meet the calibration conditions: MBE ±5%, CV RMSE &lt; 15% and R2 &gt; 0.75. For the analyzed RST model, the following values of evaluation indicators were obtained: MBE = −1.1%, CV RMSE = 11.8% and R2 = 0.91. The evaluation results obtained gave rise to the conclusion that the method used, which is based on a limited amount of data describing buildings, gives good results in estimating the unit rate of energy demand for heating.

Assessing Indoor Environmental Quality in a Crowded Low-Quality Built Environment: A Case Study

Home heating, cooling and ventilation are a major concern for those living in low-quality built environments, particularly those with high occupancy rates (crowded houses). In New Zealand, both owner-occupiers and tenants can experience problems associated with poor Indoor Environmental Quality (IEQ), such as poor thermal comfort and dampness, when Heating Ventilation and Air-Conditioning (HVAC) systems are not installed, improperly installed or too expensive to run. Occupants of poorer households are the most affected by high installation or running costs of HVAC systems, and are also more likely to live in households with a higher level of crowding. Poor IEQ in housing is associated with adverse health outcomes, particularly respiratory illness. This paper outlines the IEQ problems experienced by households living in an area of New Zealand with higher levels deprivation and shows how an HVAC system could be employed to remedy poor IEQ. This report presents a case study of a house with poor IEQ that was selected from a survey conducted across 24 homes in the Manukau, Auckland region of New Zealand. The IEQ results are presented for this house, which performs poorly in terms of relative humidity, temperature and thermal comfort. This house is then analysed using the computational fluid dynamics (CFD) approach in ANSYS CFX 2021R1 based on the American Society of Heating, Refrigeration and Airconditioning Engineers (ASHRAE) standard 55-2017 and a model of temperature and air flow is created in the software, which can identify ways to improve these parameters in the house. These results are compared with the New Zealand Healthy Homes Standards 2019. The simulation showed the system was capable of lifting the indoor temperature to above 21 ℃, eliminating cold spots and improving thermal comfort, and reduced relative humidity to below 50%.

Teaching Factory Model Development in Vocational High Schools

This study aims to find a conceptual model of teaching factory in the field of air conditioning and air conditioning engineering in vocational high schools (VHS). The teaching factory development model is expected to have a solid legal foundation and be able to carry out independent financial management so that they are able to carry out sound business practices. This study uses a type of development research, namely research and development (R D), with a 4-D (Four-D) approach. The stages in this research are define, design, development, and disseminate. The conceptual model of the teaching factory was tested for feasibility by the validator of material experts (expert judgment) and the model user, namely by the executor of the teaching factory in the field of refrigeration and air conditioning engineering at VHS 1 Magelang. The results of the study indicate that the teaching factory conceptual model consists of components, namely 1) information technology; 2) PPK-BLUD; 3) HR; 4) block schedule; 5) worksheets; 6) products/services; 7) workshops; 8) industry partnerships; and 9) system management. Based on the results of expert validation and model user responses, the teaching factory conceptual model was declared feasible to be applied in VHS. The teaching factory conceptual model has a solid legal foundation, allows for independent financial management patterns, and can carry out healthy business practices on an ongoing basis (sustainability).