Arnas Lubis | Waseda University (original) (raw)

Papers by Arnas Lubis

Over the years, researchers have been developing different ventilation strategies as a potential ... more Over the years, researchers have been developing different ventilation strategies as a potential solution for controlling infectious airborne transmissions in healthcare facilities. The effects of ventilation systems on airflow characteristics have been extensively discussed among researchers since SARS-CoV-2 outbreak in 2019. Based on a bibliometric study of 154 publications from 1970 to 2021 retrieved from the Web of Science (WoS) database, this paper examines the research landscape on the effects of ventilation strategies on airflow analysis in healthcare facilities. Results show that China is the most productive country due to its significant contributions to the top prolific authors and funding agencies, which have promoted the research development of the topic. Several research hotspots were identified through keyword co-occurrence analysis. Cluster 1 highlights the ventilation studies involving ventilation layouts and ventilation rates in healthcare facilities. Cluster 2 unde...

Applied Thermal Engineering

Solar thermal cooling system was installed on Mechanical Research Center (MRC) Building that is l... more Solar thermal cooling system was installed on Mechanical Research Center (MRC) Building that is located in Universitas Indonesia, Depok, Indonesia. It is the first cooling system in Indonesia that utilizes solar energy as energy input combined with natural gas; therefore, the control system must be appropriated with the climates. In order to stabilize the cooling capacity and also to maximize the use of solar energy, the system applies some controllers. Constant flow rate and on/off controller are applied for the hot water, chilled water and cooling water pumps. The hot water circulated by pump when the solar radiation is over than 400W/m<sup>2</sup>, and the chilled water is continually circulated by pump and its temperature is kept constant 7 °C by absorption chiller. The cooling water is also continually circulated until the outlet temperature of cooling tower below than 27 <sup>o</sup>C. Furthermore, the three-way valve is used to control the hot water fo...

Renewable Energy and Power Quality Journal, 2020

A simulation approach to heat pump systems is proposed in this paper. The evaluation of working f... more A simulation approach to heat pump systems is proposed in this paper. The evaluation of working fluids is conducted. Some alternative refrigerants, including R245fa, R32, R1234ze, and R1224yd are investigated. Moreover, the selected refrigerants are used in the simulation. The simulation is conducted using MATLAB software. Subsequently, the system is analyzed in terms of the coefficient of performance (COP) and exergy efficiency. The results indicate that R1224yd is the best refrigerant with regards to safety, environmental impact, and physical properties. Based on the energy and exergy analysis, R1224yd can attain a COP of 6.5 and exergy efficiency of 29.8%.

IOP Conference Series: Earth and Environmental Science, 2021

Many researches have been conducted on cooling equipment to reduce its energy consumption, mainte... more Many researches have been conducted on cooling equipment to reduce its energy consumption, maintenance and operation cost. Oil-free chiller uses a magnetic bearing compressor to avoid friction loss from the bearing’s contact surface. In comparison to a conventional compressor, the magnetic bearing of the motor, with the help of variable speed drive (VSD), runs more efficiently at partial loads. This paper presents the application of oil-free compressors in a chiller plant. The chiller plant also includes a chilled water system. In designing an energy-efficient air conditioning system it is important to choose proper chilled water and cooling water system. The evaporator is used to absorb the heat from the conditioned room while the condenser rejects the heat from the chiller to the environment through circulating cooling water. This research also aims to analyze the chiller plant for the air conditioning system operates in one of the shopping malls in Indonesia and how it affects th...

Sistem pendingin konvensional untuk pengkondisian udara pada bangunan gedung yang menggunakan flu... more Sistem pendingin konvensional untuk pengkondisian udara pada bangunan gedung yang menggunakan fluida kerja serta sumber energi yang dikategorikan tidak ramah lingkungan maka bertanggungjawab langsung terhadap efek rumah kaca dan penipisan lapisan ozon. Implementasi konsep baru berlanjut di dalam sistem pengkondisian udara pada bangunan gedung adalah hal yang sangat krusial. Sistem pendinginan absorpsi yang memanfaatkan energi panas matahari (energi terbarukan) memiliki keuntungan, yaitu menggunakan fluida kerja yang ramah lingkungan seperti air atau berupa larutan garam kemudian sumber energi yang bersih dan ramah lingkungan. Potensi energi matahari yang besar di Indonesia menyebabkan sistem ini sangat memungkinkan untuk diimplementasikan. Oleh karena itu studi mengenai pengujian sistem ini pada kondisi cuaca di Indonesia dilakukan. Selain itu, pada akhirnya, studi ini juga dapat mengetahui besar konsumsi energi keseluruhan dan emisi gas CO2. Pada studi ini dipaparkan hasil pengujia...

Energy and Buildings, 2018

The energy demand of the commercial building sector is largely for cooling and heating and will e... more The energy demand of the commercial building sector is largely for cooling and heating and will eventually result in energy and environmental crises; therefore, enhancing the performance of the cooling and heating systems used in buildings is paramount. In response to this need, focus was set on the gas enginedriven heat pump-combined system (GHPC)-consisting of a gas engine, single-stage vapour compression system, and single-effect absorption system-that saves more energy as compared to a conventional gas engine-driven heat pump. However, so far, only the performance and transient characteristics of a fabricated GHPC have been investigated. Therefore, to ascertain the characteristics of the GHPC startup dynamics under unsteady state operations so as to achieve efficient and stable start-up operation, experiments and simulations were attempted in this study. The transient behaviour from the start-up of this combined system in cooling and heating operating modes was also scrutinized. Accordingly, it was found that simulation results agreed well with experimental data. It was concluded that there were no large delayed responses in the absorption system during start-up operation when start-up of the absorption system is considered based on the system cooling capacity response after the solution pump starts.

Applied Thermal Engineering, 2020

• Operation strategy of solar-gas fired absorption cooling system is presented. • Optimal and saf... more • Operation strategy of solar-gas fired absorption cooling system is presented. • Optimal and safe operation of single/double-effect water/LiBr chiller is analysed. • Chilled water outlet is well maintained around 7°C with 25 m 3 /h constant flow rate. • The field test thermal and electrical COPs are around 0.9-1.1 and 4.5-5.5. • Solar-gas fired absorption system operated with a solar fraction of 0.25-0.72.

Case Studies in Thermal Engineering, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

International Journal of Technology, 2019

This paper investigates the use of two low global warming potential working fluids, HCFO-1224yd(Z... more This paper investigates the use of two low global warming potential working fluids, HCFO-1224yd(Z) and HCFO-1233zd(E), in high-temperature heat pump systems. A simulation was performed at evaporating temperatures ranging from 50-70°C and a condensing temperature of 110°C. A solar thermal collector was used to supply the energy needs on the evaporator side. Energy, exergy, and environmental analyses were performed to evaluate both environmentally friendly refrigerants and compare them to HFC-245fa. The coefficient of performance (COP) and total exergy destruction represented the performance of the system, while the total equivalent warming impact was used to evaluate the environmental effect of each refrigerant. At an evaporation temperature of 50°C, HCFO-1224yd(Z) and HCFO-1233zd(E) showed comparable performance to R245fa, with COP values of about 2.74 and 2.69, respectively (R245fa had a COP value of about 2.66). The same results were also obtained at evaporation temperatures of 60°C and 70°C, at which R1224yd showed good performance compared to R1233zd and R245fa with COP values of 3.6 for 50 o C evaporation temperature and 4.75 for 70 o C evaporation temperature. Additionally, both suggested refrigerants had low direct emission compared to R245fa based on the results from the environmental analysis.

International Journal of Air-Conditioning and Refrigeration, 2019

The objective of this study is to analyze all the energy used in the solar cooling system in Univ... more The objective of this study is to analyze all the energy used in the solar cooling system in Universitas Indonesia. This system uses three energies at the same time, namely, solar, gas and electricity energies, which are used to provide a required cooling capacity from the mechanical research center (MRC) building in Universitas Indonesia. The single–double-effect absorption chiller is the main component of the solar thermal cooling system to provide the chilled water that is circulated between the system and MRC building. In this system, heat from solar energy is absorbed by the evacuated tube solar collector and then transferred to the hot water that is used to generate vapor together with the gas at the absorption machine. On the other hand, electricity is mostly consumed by the pumps to circulate the hot, cooling and chilled water, also the working fluids inside the absorption machine. Finally, all the energies used to create a thermal comfort zone in the MRC building based on t...

Case Studies in Thermal Engineering, 2019

In this paper, a method to predict the performance of an absorption chiller using solar thermal c... more In this paper, a method to predict the performance of an absorption chiller using solar thermal collectors as the energy input is analyzed rigorously. Artificial Neural Network (ANN) is developed based on experimental data to predict the performance of the solar absorption chiller system at Universitas Indonesia. In order to perform ANN accurately, some parameters such as chilled water inlet and outlet temperatures, cooling water inlet and outlet temperatures, solar hot water inlet and outlet temperatures, hot water inlet and outlet temperatures, ambient temperature and fuel consumption flow rate are chosen as the input variables. In addition, a Principle Component Analysis (PCA) is used to reduce the number of input variables for performance prediction. Without sacrificing the ANN's prediction accuracy, PCA identified the sensitive variables from all input variables. The developed ANN model combined with PCA (ANN + PCA) shows good performance which has a comparable error with ANN model, specifically the configuration 9-6-2 (9 neurons, 6 inputs, 2 outputs) of the ANN + PCA model leads to a COP root-mean-square error of 0.0145.

Energy Conversion and Management, 2017

As widely known, some industrial processes produce a large amount of waste heat while others requ... more As widely known, some industrial processes produce a large amount of waste heat while others require a large amount of steam to heat the process flow. The main difference involves the temperature level of these heat quantities. Absorption heat transformers play a strategic role in waste heat recovery and heat supply to manufacturing processes due to their ability to utilize heat at a certain temperature level and release the enthalpy of mixing of the refrigerant at a different temperature level with a negligible amount of mechanical work input. However, given the lack of examples that find application as operative plants, the feasibility of the technology is questioned in academic and technical domains. In this study, the operability of a double-lift absorption heat transformer that generates pressurized steam at 170°C is studied across a full range of operative conditions. The results demonstrate and clarify the manner in which the system can operate steadily and efficiently when driven by hot water temperature at approximately 80°C while safely generating steam at a temperature exceeding 170°C. The conditions yielding maximum system efficiency and capacity are identified, and the obtained experimental results are used to define an optimal control strategy.

International Journal of Technology, 2016

Indonesia's economic growth has continued at a steady rate of approximately 5% to 6% annually, an... more Indonesia's economic growth has continued at a steady rate of approximately 5% to 6% annually, and energy consumption in the entire country has been increasing year by year. Demand for air conditioning in buildings is expanding. In line with this expansion, a 239 kW solar airconditioning system using a single-double effect combined absorption chiller was installed in a building at the University of Indonesia's Faculty of Engineering located in Depok city, near Jakarta, with the aim of reducing greenhouse gas emissions. We collected and analyzed data from this airconditioning system to better comprehend its performance. We report the outline and the performance of the chiller and the airconditioning system.

Applied Thermal Engineering, 2016

Local entropy generation analysis of an absorptive film on a cooled horizontal tube. • Parametric... more Local entropy generation analysis of an absorptive film on a cooled horizontal tube. • Parametric study of the entropy generation related to various irreversibility sources. • Identification of the least irreversible solution mass flow-rate. • Parameters accounting for the irreversibility are used as optimization criterion.