Numerical Approach to Study Nonuniform Gas–Liquid Distribution in the Refrigerant Distributor in an Air Conditioner

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Eiji Ishii ◽  
Masanori Ishikawa ◽  
Kazuki Yoshimura
Keyword(s):  
Uniform Distribution ◽  
Grid Method ◽  
Particle Method ◽  
Numerical Approach ◽  
Liquid Films ◽  
Air Conditioner ◽  
Liquid Interfaces ◽  
Liquid Distribution ◽  
Air Conditioners ◽  
Nonuniform Gas

Factors that influence the nonuniform gas–liquid distribution in refrigerant distributors in air conditioners were studied. Gas–liquid flows in two-pass and multipass distributors were numerically simulated with a particle/grid hybrid method; droplets and liquid films were mainly simulated using a particle method, and gas flows were simulated using a grid method. Complex behaviors of multiscale gas–liquid interfaces in the multipass distributor were simulated because droplets that were smaller than the grid size could be simulated without numerical diffusion through the gas–liquid interfaces. The effect of the connecting angle of the bend pipe was studied in the two-pass distributor, whereas the effect of the tube's position relative to the distributor inflow and the effect of gravity were investigated in the multipass distributor. The model was validated against multiple experimental data taken from an at-scale physical model. We found that the direction of gravity plays a role in ensuring a uniform distribution of liquid in the multipass distributor for ensuring a uniform distribution.

Study of Factors Influencing Non-Uniform Gas-Liquid Distribution in the Refrigerant Distributor in an Air Conditioner

2014 ◽  
Author(s):  
Eiji Ishii ◽  
Kazuki Yoshimura
Keyword(s):  
Grid Method ◽  
Particle Method ◽  
Liquid Films ◽  
Gas Flows ◽  
Air Conditioner ◽  
Liquid Interfaces ◽  
Liquid Distribution ◽  
Air Conditioners ◽  
Multi Scale ◽  
Liquid Flows

Factors that influence the non-uniform gas-liquid distribution in refrigerant distributors in air conditioners were studied. Gas-liquid flows in two-pass and multi-pass distributors were numerically simulated with a particle/grid hybrid method; droplets and liquid films were mainly simulated using a particle method, and gas flows were simulated using a grid method. Complex behaviors of multi-scale gas-liquid interfaces in the multi-pass distributor were simulated because droplets that were smaller than the grid size could be simulated without numerical diffusion through the gas-liquid interfaces. The effect of the connecting angle of the bend pipe was studied in the two-pass distributor, whereas the effects of the tube’s position relative the distributor inflow and the effect of gravity were investigated in the multi-pass distributor. The model was validated against multiple experimental data taken from an at-scale physical model. We found that keeping the liquid at the inlets of the multi-pass tubes was important for ensuring a uniform distribution.

Hybrid Particle/Grid Method for Predicting Motion of Micro- and Macrofree Surfaces

2006 ◽  
Vol 128 (5) ◽  
pp. 921-930 ◽  
Author(s):  
Eiji Ishii ◽  
Toru Ishikawa ◽  
Yoshiyuki Tanabe
Keyword(s):  
Liquid Film ◽  
Volume Fraction ◽  
Grid Method ◽  
Particle Method ◽  
Liquid Films ◽  
Liquid Column ◽  
Computational Time ◽  
Fuel Injector ◽  
Hybrid Particle ◽  
Liquid Flows

We developed a method of hybrid particle/cubic interpolated propagation (CIP) to predict the motion of micro- and macrofree surfaces within gas-liquid flows. Microfree surfaces (smaller than the grid sizes) were simulated with the particle method, and macrofree surfaces (larger than the grid sizes) were simulated with the grid method (CIP is a kind of grid method). With the hybrid, velocities given by the advection part of the particle method were combined with those given by the advection part of CIP. Furthermore, the particles used with the particle method were assigned near the macrofree surfaces by using the volume fraction of liquid that was calculated with CIP. The method we developed was used to predict the collapse of a liquid column. Namely, it was simultaneously able to predict both large deformation in the liquid column and its fragmentation, and the predicted configurations for the liquid column agreed well with the experimentally measured ones. It was also used to predict the behavior of liquid films at the outlet of a fuel injector used for automobile engines. The particle method in the simulation was mainly used for liquid films in the air region and the grid method was used for the other regions to shorten the computational time. The predicted profile of the liquid film was very sharp in the air region where the liquid film became thinner than the grid sizes; there was no loss of liquid film with numerical diffusion.

Simulation of Liquid Jet Breakup Using a Combination of Particle and Grid Methods

2005 ◽  
Author(s):  
Eiji Ishii ◽  
Toru Ishikawa ◽  
Yoshiyuki Tanabe
Keyword(s):  
Liquid Film ◽  
Computation Time ◽  
Grid Method ◽  
Particle Method ◽  
Liquid Films ◽  
Liquid Jet ◽  
Computational Domain ◽  
Fuel Injector ◽  
Automobile Engine ◽  
Numerical Diffusion

Fine atomization of the liquid jet from a fuel injector in an automobile engine lowers engine emissions and improves fuel efficiency. The breakup length of liquid films and the lengths of ligaments near the injector outlet after the breakup of liquid films are important parameters for predicting the atomization. These parameters have been predicted mainly using the Eulerian-grid method. (We refer to this as the ‘grid method’.) However, the grid method causes a loss of the liquid film with numerical diffusion, and it requires a large amount of computation time in practical engineering aspect because fine meshes smaller than the ligaments must be used. On the other hand, the particle method, an alternative (particle-based) method for representing the continuum Navier-Stokes equation which can simulate a ligament using a group of particles, does not cause numerical diffusion. However, a large number of particles are needed to simulate the entire computational domain within the injectors. In this study, we have focused on the flow field only near the injector outlet, and have tried to simulate the breakup of liquid films by using groups of particles in the particle method. In the simulation, the particle method was applied only to the liquid film and the grid method was used in other regions to shorten the computation time. Furthermore, we tried to integrate Brackbill’s surface-tension model, which is widely used in the grid method, into the particle method. To evaluate this approach, we compared the breakup lengths obtained for a cylindrical liquid jet in a uniform air stream with measurements done by Arai and Hashimoto; the breakup lengths agreed well with their measurements. We then simulated the breakup of a liquid film near the outlet of a fuel injector used for automobile engine, and found that our hybrid method could simulate the breakup of the liquid film into ligaments.

scholarly journals Optimal Air Conditioner Placement Using a Simple Thermal Environment Analysis Method for Continuous Large Spaces with Predominant Advection

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4663
Author(s):  
Tatsuhiro Yamamoto ◽  
Akihito Ozaki ◽  
Myonghyang Lee
Keyword(s):  
Air Conditioning ◽  
Thermal Environment ◽  
Fluid Dynamic ◽  
Optimal Placement ◽  
Air Conditioner ◽  
Analysis Method ◽  
Computational Fluid Dynamic Analysis ◽  
Environment Analysis ◽  
Air Conditioners ◽  
Energy Simulations

The number of houses with large, continuous spaces has increased recently. With improvements in insulation performance, it has become possible to efficiently air condition such spaces using a single air conditioner. However, the air conditioning efficiency depends on the placement of the air conditioner. The only way to determine the optimal placement of such air conditioners is to conduct an experiment or use computational fluid dynamic analysis. However, because the analysis is performed over a limited period, it is difficult to consider non-stationarity effects without using an energy simulation. Therefore, in this study, energy simulations and computational fluid dynamics analyses were coupled to develop a thermal environment analysis method that considers non-stationarity effects, and various air conditioner arrangements were investigated to demonstrate the applicability of the proposed method. The accuracy verification results generally followed the experimental results. A case study was conducted using the calculated boundary conditions, and the results showed that the placement of two air conditioners in the target experimental house could provide sufficient air conditioning during both winter and summer. Our results suggest that this method can be used to conduct preliminary studies if the necessary data are available during design or if an experimental house is used.

Self-Assembly of Monolayers of Submicron Sized Particles on Thin Liquid Films

2013 ◽  
Author(s):  
Shriram Pillapakkam ◽  
N. A. Musunuri ◽  
P. Singh
Keyword(s):  
Electric Field ◽  
Self Assembly ◽  
Uv Light ◽  
Capillary Forces ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Liquid Interfaces ◽  
Uv Curable ◽  
Particle Monolayer ◽  
Uv Curable Resin

In this paper, we present a technique for freezing monolayers of micron and sub-micron sized particles onto the surface of a flexible thin film after the self-assembly of a particle monolayer on fluid-liquid interfaces has been improved by the process we have developed where an electric field is applied in the direction normal to the interface. Particles smaller than about 10 microns do not self-assemble under the action of lateral capillary forces alone since capillary forces amongst them are small compared to Brownian forces. We have overcome this problem by applying an electric field in the direction normal to the interface which gives rise to dipoledipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another liquid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film.

Solar Heat Underground Storage Based Air Conditioning Vis-à-Vis Conventional HVAC Experimental Validation

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Carlos R. de Nardin ◽  
Felipe T. Fernandes ◽  
Adriano J. Longo ◽  
Luciano P. Lima ◽  
Felix A. Farret ◽  
...  
Keyword(s):  
Air Conditioning ◽  
Heat Pumps ◽  
Conventional Heating ◽  
Management Technique ◽  
Air Conditioner ◽  
Heat Management ◽  
Air Conditioners ◽  
Solar Heat ◽  
Reduction Of Energy Consumption ◽  
The One

This paper presents a comparison of air conditioners using the conventional heating, ventilation, and air conditioning heat pumps and the one using solar heat stored underground, also known as shallow geothermal air conditioning. The proposed air conditioner with solar heat stored underground reunites practical data from an implementation of the heuristic perturb-and-observe (P&O) control and a heat management technique. The aim is to find out the best possible heat exchange between the room ambient and the underground soil heat to reduce its overall consumption without any heat pump. Comparative tests were conducted in two similar rooms, each one equipped with one of the two types of air conditioning. The room temperature with the conventional air conditioning was maintained as close as possible to the temperature of the test room with shallow geothermal conditioning to allow an acceptable data validation. The experiments made both in the winter of 2014 and in the summer of 2015 in Santa Maria, South Brazil, demonstrated that the conventional air conditioner consumed 19.08 kWh and the shallow geothermal conditioner (SGC) consumed only 4.65 kWh, therefore, representing a reduction of energy consumption of approximately 75%.

Performance evaluation and design considerations for a split air-conditioner with built-in thermal energy storage

2018 ◽  
Vol 40 (5) ◽  
pp. 560-575
Author(s):  
Jehanzeb Ahmad ◽  
M Najam Ul Islam ◽  
Jawwad Sabir
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Low Cost ◽  
Hvac Systems ◽  
Air Conditioner ◽  
Widespread Application ◽  
Air Conditioners

The benefits of thermal energy storage using phase change materials are well documented in the literature. Despite all the potential benefits of thermal energy storage, its commercial and widespread application remains limited. This is due to the high initial cost of phase change materials, extensive rework required in buildings, major modifications in HVAC systems, and the potential for leakage, fire and toxicity hazards. There is a strong need for a simple thermal energy storage solution which can be adopted by large number of consumers. Ductless split air-conditioners are portable, low cost, efficient and account for 70% of all air-conditioning systems sold worldwide each year. The present research provides a novel and low cost solution that incorporates thermal energy storage in these air conditioners, allowing them to run without electricity for 3 h. The paper deals with the detailed design aspects and engineering challenges that arise when incorporating thermal energy storage in these small units. A prototype air-conditioner with in-built thermal energy storage was developed, and all performance parameters presented have been validated through data obtained from the prototype. Our results indicate that thermal energy storage can be incorporated in split units in low cost and with minimal drop in overall energy efficiency of the system. Practical application: Incorporating thermal energy storage in split air-conditioners which enables them to run without grid for many hours has immense practical applications. Since around 50% power in any building is consumed by HVAC systems, being able to provide cooling during peak hours without using grid can significantly reduce load on the grid without compromising user comfort. For developing countries where load shedding is frequent, the users can run these air-conditioners without the use of generators or batteries thus saving costs and the environment.

scholarly journals KINERJA TERMAL SELUBUNG GEDUNG KULIAH KOTA BANDAR LAMPUNG ITERA

2019 ◽  
Vol 3 (3) ◽  
pp. 267
Author(s):  
Andi Asrul Sani ◽  
Adelia Enjelina Matondang ◽  
Guruh Kristiadi Kurniawan ◽  
Anggi Mardiyanto
Keyword(s):  
Heat Transfer ◽  
Energy Consumption ◽  
Building Energy ◽  
Air Conditioner ◽  
Tropical Country ◽  
Air Conditioners ◽  
Natural Lighting ◽  
Thermal Transfer ◽  
Institute Of Technology ◽  
Window Area

Abstract: The use of glass material should consider the comfort of space in the building. Field of glass is needed as natural lighting and visual facilities between the occupants and the surrounding environment. Its function as natural lighting is often accompanied by an increase in temperature in buildings, considering that Indonesia is a tropical country. Building temperatures that increase due to incoming sunlight can cause discomfort to building occupants. Such conditions make building occupants use air conditioner (AC). The use of air conditioners can increase the value of building energy consumption. For this reason, research on the value of heat transfer in buildings or the value of OTTV (Overall Thermal Transfer Value). OTTV value calculation is done by manual calculation. Bandar Lampung City lecture building at the Sumatra Institute of Technology was chosen as the object of this study. From the results of the study found that the value of heat transfer of a building or OTTV (Overall Thermal Transfer Value) is influenced by the factor of the ratio of the window area to the facade or WWR (Window Wall Ratio) and the shading factor (Shading Coefficient).(Keywords: Keyword: energy consumption, building energy, glass. Abstract: Penggunaan material kaca semestinya mempertimbangkan kenyamanan ruang dalam bangunan. Bidang kaca diperlukan sebagai pencahayaan alami dan sarana visual antara penghuni dan lingkungan sekitar. Fungsinya sebagai pencahayaan alami seringkali disertai dengan peningkatan temperatur pada bangunan, mengingat Indonesia merupakan negara yang beriklim tropis. Temperatur bangunan yang meningkat akibat dari radiasi sinar matahari yang masuk dapat menyebabkan ketidaknyamanan bagi penghuni bangunan. Kondisi seperti itu membuat penghuni bangunan menggunakan air conditioner (AC). Penggunaan air conditioner tersebut dapat meningkatkan nilai konsumsi energi bangunan. Untuk  itu dilakukan penelitian mengenai nilai perpindahan panas dalam bangunan atau nilai OTTV (Overall Thermal Transfer Value). Penghitungan nilai OTTV dilakukan dengan penghitungan manual. Gedung kuliah Kota Bandar Lampung di Institut Teknologi Sumatera di pilih sebagai objek dalam penelitian ini. Dari hasil penelitian ditemukan bahwa nilai perpindahan panas suatu bangunan atau OTTV (Overall Thermal Transfer Value) dipengaruhi oleh faktor nilai perbandingan luas jendela terhadap bidang fasad atau WWR (Window Wall Ratio) dan faktor pembayangan (Shading Coefficient).Kata kunci : konsumsi energi, energi bangunan, kaca.

Psycho-physiological evaluations of low-level impulsive sounds produced by air conditioners

2021 ◽  
Vol 263 (5) ◽  
pp. 1186-1193
Author(s):  
Yoshiharu Soeta ◽  
Ei Onogawa
Keyword(s):  
Sound Pressure ◽  
Living Room ◽  
Air Conditioner ◽  
Regression Analyses ◽  
Noise Sources ◽  
Air Conditioners ◽  
Low Level ◽  
Subjective Loudness ◽  
Long Time

Air conditioners are widely used in buildings to maintain thermal comfort for long time. Air conditioners produce sounds during operation, and air conditioners are regarded as one of the main noise sources in buildings. Most sounds produced by the air conditioner do not fluctuate over time and sound quality of the steady sounds produced by the air conditioner have been evaluated. However, air conditioners sometimes produce low-level and impulsive sounds. Customers criticizes such sounds are annoying when they sleep and they spend time quietly in the living room. The aim of this study was to determine the factors that significantly influence the psycho-physiological response to the low-level impulsive sounds produced by air conditioners. We assessed the A-weighted equivalent continuous sound pressure level (LAeq) and factors extracted from the autocorrelation function (ACF). Subjective loudness, sharpness, annoyance, and electroencephalography (EEG) were evaluated. Multiple regression analyses were performed using a linear combination of LAeq, the ACF factors, and their standard deviations. The results indicated that LAeq, the delay time of the first maximum peak, the width of the first decay of the ACF, and the magnitude and width of the IACF could predict psycho-physiological responses to air conditioner sounds.

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