Nat Kasayapanand

Effect of the Electrode Arrangements in a Tube Bank on the Characteristic of Electrohydrodynamic Heat Transfer Enhancement: Low Reynolds Number

Enhancement in heat transfer using the electrohydrodynamic (EHD) technique is numerically examined in laminar forced convection across a tube bank with six different wire electrode arrangements. The electric field is generated by the wire electrodes charged with high DC voltages ranging from 7.5 to 17.5 kV. The Reynolds number corresponding to the flow considered is between 100 and 1,500. The numerical modeling of the laminar forced convection includes the interactions among the electric field, the flow field, and the temperature field. It is found that the heat transfer is significantly enhanced by the EHD at a low Reynolds number, and the short distance between the wire electrodes and the tube surface from which different electrode arrangements are reported for aligned and staggered tube configurations. The value Nu/Nu 0 of an aligned configuration increases from row to row and appears to be similar with that of a staggered configuration.

Technical and economical assessment of energy-saving roof and wall construction in Thailand

This research assessed the economic impact and construction costs of buildings with solar chimneys in Thailand, called bioclimatic houses. A solar chimney uses a combination of air gaps between walls and roof, and effective ventilation to lower the indoor temperature and reduce the need for air conditioning. The study looked at small, medium, and large size houses and studied construction techniques, the materials used, and the time needed to build a residential structure. It also polled owners of bioclimatic houses about their satisfaction. The techniques employed in building bioclimatic houses take slightly longer and cost slightly more than those used in standard construction. However, the study found that bioclimatic houses use approximately 10–20% less electricity for air conditioning require less maintenance and have a payback period of 6–13 years, depending on the size. The lifespan of insulation material used in standard houses is about 20–25 years, while the lifespan of a solar chimney is about 40–50 years. The solar chimney concept can also be applied to standard houses with minimal renovation. The study found that this type of house was suitable for use in Thailand, and with increased consumer awareness, had a high probability for adoption.

A design and assessment of solar chimney of bioclimatic house wall and roof for construction in the housing market of Thailand

This research is a design and assessment of a bioclimatic house wall and roof to be constructed in Thailand’s housing market in order to provide information for potential builders as well as the peace of mind of the owner. The research found that a bioclimatic house with a double-layered solar chimney is appropriate for use in Thailand throughout the year. It lowers the average internal temperature of the house by approximately 1–2℃ when compared to the energy-saving material used in a normal building. Bioclimatic construction also creates natural ventilation, heat removal, and can reduce indoor temperature. It also comes with an easy-to-build design to facilitate construction and can save house energy consumption. Practical application : This research provides helpful information of solar chimney wall and roof for both the owners and developers in adopting an energy-efficient house for sustainable energy conservation. A solar chimney of a bioclimatic house is a highly interesting alternative for saving energy in the long term. When properly promoted, it will help save a huge amount of energy throughout Thailand and tropical area, and serve to promote the cause of global environmental conservation into the future.

Electrohydrodynamic Induced Flow and Heat Transfer in Vertical Channel with Fin Array Attached

Electrohydrodynamic heat transfer enhancement of natural convection inside the finned vertical channels is investigated via a computational fluid dynamics technique. The interactions between electric field, flow field, and temperature field are numerically determined. Flow and heat transfer enhancements are significantly influenced at low Rayleigh number. The effect of electrode arrangement and number of electrodes to the average velocity and Nusselt number are expressed. An optimum inclined angle of the channel is recommended. Relation between the number of fins and fin length to the augmented flow and heat transfer is also analyzed.

The Development of Polyethylene Naphthalate Films by Low-pressure High-frequency Plasma Chemical Vapor Deposition System with Advance Oxidations Process

Abstract The low-pressure high-frequency plasma chemical vapor deposition (CVD) system was developed with non-thermal plasma process to study the Polyethylene naphthalate (PEN) surface characteristics. Plasma surface treatment by oxygen can improve the adhesive properties. A mixture of Ar and O2 gas was used in the plasma treatment. The oxygen gas flow rate was between 0.1 L/min and 0.5 L/min, whereas the Ar gas flow rate was set at 10 L/min. The surface was investigated by contact angle meter and X-ray photoelectron spectroscopy (XPS) to determine the differences between untreated and treated surfaces. The results indicated that the low-pressure high-frequency plasma chemical vapor deposition system could be used for surface modification.

Low-Temperature Naturatron Sputtering System for Deposition of Indium Tin Oxide Film

In this paper, we have newly developed a metal thin film-forming sputtering system using the Naturatron Sputtering method that can prevent the plastic film from suffering damage caused by the high-energy particles in plasma and carry out the low-temperature high-density metal deposition with a sputtering chamber and a film deposition chamber separated from each other. This system has made it possible to deposit the indium tin oxide (ITO) thin film on the poly(ethylene naphthalate) film as a substrate. As a result of energy-dispersive X-ray spectroscopy analysis or scanning electron microscope analysis performed for the ITO thin film, it has been proven that the uniform-surface ITO thin film can be deposited on a plastic film.

Utilization of photovoltaic for broadband satellite communications in rural area of Thailand

Electricity, Information and Communication Technologies (ICTs) are very important not only in urban areas but also in rural areas. To provide ICTs service in rural areas, sources of electricity and communication infrastructures must be implemented. Electricity is a major condition due to the fact that all electronic devices needed it in order to power on, so that it is impossible to operate any forms of ICTs in areas where the main national grid line is unavailable. Almost rural areas of Thailand where the main national grid line is unavailable have very good sunlight intensity. Photovoltaic is the most effective renewable energy technologies in those areas for meeting electricity needed in areas that are not connected to the main national grid line. In this paper, the efficiency utilization of photovoltaic as source of electricity for broadband satellite communication systems as well as social and economic impact and quality of life of people in rural areas of Thailand are presented. The results show that most rural communities would be able to universally access to the basic telecommunications services such as internet access and public telephone via satellite communication systems. However, in some field case study, broadband internet access via satellite communication may be unnecessary for some rural communities and the most exactly rural communities needed are electricity for household usage and battery charger.

Exact Solution of Concentric Rotating Disk System

The exact stress, strain, and displacement components of triple-composite rotating disks from different composite materials are investigated analytically. The plane stress problem in elasticity is considered for the concentric disks subjected to a uniform angular velocity. Boundary conditions, conditions at the interface, and mathematical conditions are discussed in conjunction with the theory of infinitesimal linear elasticity. The stress function is conducted individually for each material. The obtained exact solutions are validated by reduction to the benchmark solutions: rotating annular disk and rotating solid disk. Some numerical results of the radial and tangential stresses are also presented accordingly. K e y w o r d s : Rotating disk; Composite disks; Multiple disks; Stress function; Plane stress