Chi Ming Lai

The influence of an architectural design alternative (transoms) on indoor air environment in conventional kitchens in Taiwan

Abstract This study intends to investigate indoor air environment via the flow fields, temperature fields and air contaminant (carbon monoxide) distributions in the conventional residential kitchens, and look for effective methods to solve those problems through natural ventilation techniques. Numerical simulations of the physical problem under consideration have been performed via a finite volume method for solving the governing equations and boundary conditions. It is obvious that location of accumulation of air contaminants is highly relevant to the location of gas fires, and using the residential range hood will be successful in eliminating air contaminants. An architectural design alternative, utilizing transoms, is proposed to improve indoor air environment in kitchens.

A METHODOLOGY TO ASSESS THE INDOOR ENVIRONMENT IN CARE CENTERS FOR SENIOR CITIZENS

Abstract A developed method for 24-h continuous measurement of indoor environment characteristics was applied to investigate care centers for aged people. The purpose was to establish the methodology to assess indoor environment characteristics at an arrangement of negative influence. The method was allowed to monitor carbon monoxide conc., carbon dioxide conc., airborne dust conc., air velocity, air temperature, relative humidity, noise level and illuminance. The magnitude of those factors mentioned above are categorized into several grades, respectively, according to the comparison with recommended (health related) values. Close congruence with the field-measured results shows the validity of questionnaire. The results show that “Noise Level” and “Relative Humidity” is represented as two significant negative-influencing factors in care centers for aged people in winter in Taiwan.

The Influence of Horizontal Longitudinal Vibrations and the Condensation Section Temperature on the Heat Transfer Performance of a Heat Pipe

This study is primarily focused on the influence of horizontal longitudinal vibrations and the condensation section temperature on the heat transfer performance of a grooved cylindrical copper heat pipe, with a length of 600 mm and an outer diameter of 8 mm. Longitudinal vibrations with frequencies of 3, 4, 5, 6, and 9 Hz and amplitudes of 2.8, 5, 10, 15, 20, and 25 mm, which would give accelerations in the range of 0.1–1.01 g, were experimentally tested. The condensation section temperature was set at 20, 30, or 40°C. A heating jacket and a cooling sleeve were installed at the evaporation and condensation sections of the test cell to mimic a constant heat flux and a constant temperature boundary, respectively. When the heat pipe started to vibrate horizontally in the longitudinal direction, this vibration caused an increase in the heat transfer of the heat pipe that was directly proportional to the input vibration energy below 500 mm2 Hz2. When the value of the vibration energy exceeded this value, the heat transfer enhancement per unit vibration energy decreased rapidly. Along with the decrease in the condensation section temperature, the average temperature of the heating section decreases. The influence of the condensation section temperature on the maximum heat transfer is much greater than that of the vibrations.

Energy Efficiency and Ventilation Performance of Ventilated BIPV Walls

Abstract This study integrated building structure, heat flow mechanism and photovoltaic system to propose ventilated building-integrated photovoltaic walls. Energy efficiency of the BIPV walls was investigated via engineering considerations and computational fluid dynamics simulations. The results showed that either the flow pattern at the lower part of the channel or the indoor vent height can affect the indoor vent flow rate. When the indoor vent position was lowered and the airflow channel was widened, the indoor vent flow rate was affected by the outdoor wind velocity. As the indoor vent height increased, the induced air velocity through the indoor vent decreased. Correlations for predicting the heat removal rate and indoor heat gain were introduced.

Experimental Investigations of Fire Spread and Flashover Time in Office Fires

The characteristics of, prediction models for, and experimental data pertaining to flashover in full-scale room fires were first reviewed. Then, initiation, growth, full development, and decay of three office fire scenarios were experimentally explored using a 10 MW fire test facility and continuous online combustion gas analysis. The conditions for flashover were investigated and compared with correlations in the literature. The model office compartment is an aerated lightweight concrete structure with dimensions of 5 m × 6 m and with a net room height of 2.4—3.3 m. The results show that the measured minimum heat release rate at flashover is consistent with the correlations of Babrauskas [5] and McCaffrey et al. [6]. Based on the fundamental definition of flashover using the ‘energy-filling’ concept it is possible to predict the flashover time via a case-based reasoning method. However, more work is needed to further validate this concept.

The effects of cracks on the thermal stress induced by soldering in monocrystalline silicon cells

Silicon-based solar applications have tended towards the use of large, thin cells. However, an increased loss of materials occurs due to a high rate of destruction during the soldering and packaging processes. In this study, the effects of the presence of cracks on the thermal stress and stress intensity factor of the cells were explored for different aspect ratios of the soldering rods using an established finite element method. It was found that the residual stress in the cell was concentrated near the ends of the soldering rods, which coincided with the typical positions where breakage tended to occur on the cell. The residual stress on the cell increased with an increasing aspect ratio of the soldering rod. Cell damage due to cracking can be avoided by controlling the magnitude of the soldering rod’s aspect ratio.

The Influence of Alternative Layouts for Air-circulation on Airflow Patterns in the Processing Area of a Cleanroom

The particle-free conditions provided by cleanrooms are essential for many modern manufacturing industries. Cleanrooms have to be first designed, constructed, and then on-site tested to ensure they achieve their performance specification. The on-site testing needs to be continued repeatedly even at the fully operational stage. In this study, field-testing of cleanrooms looking at parameters such as: airborne particle counts, airflow volume, turbulence intensity, temperature and pressure difference, were carried out under different occupational states in a newly constructed cleanroom. It was found that improved contamination control was needed due to the high particle counts at specific sampling locations. Consequently, a computational fluid dynamics simulation was conducted to investigate airflow characteristics based on the existing field-test results. Improvement strategies with less expenditure were proposed and have been assessed comprehensively. The results from computer simulation showed that an improvement of airflow could be achieved, not only by increasing the number of fan-filter units, but also by better arrangement of the return air grilles at both sides of the cleanroom.

The Influence of Ventilation Design Mixes on the Thermal Environment in Elementary School Classrooms

The roofs of most of the buildings in Taiwan are exposed to direct (overhead) solar radiation during the summer season because it is located near the Tropic of Cancer. The estimated yearly solar heat gain received from a roof is 2.78 times greater than that gained from a south-side wall (the second highest in terms of solar heat gain). Since most elementary schools in Taiwan are not equipped with air conditioners, the classrooms, especially those located on the upper floors, are regularly overheated. Solving the problem of ventilation and improving the thermal environment in Taiwan elementary school classrooms is an important endeavor. CFD simulations were conducted to investigate six combinations of designs that can incorporate natural ventilation (double roofs, ‘‘Covered Ridge with Sidewall Opening’’ (CRSOs), roof ridge openings, and window layout) influence indoor thermal environments, especially during the summer season when the outdoor wind velocity is low. The results show that when a double roof, roof ridge openings, and a CRSO are implemented, both the ventilation performance and the thermal environment of the classrooms are improved, regardless of whether the windows are laid out in a staggered formation (high-low) or in a conventional window layout.

How a natural ventilation shaft affects smoke layer descent in room fires

Abstract In this study, full-scale experiments were conducted to observe the influence of a natural ventilation shaft on smoke layer descent in room fires. An oil pan with a heat release rate of 50 kW was ignited in a model space to generate fire smoke for the observation of smoke layer descent and flow conditions under various natural ventilation conditions. It is found that when there is no natural ventilation shaft available in a room that is on fire, the height of the descending smoke layer in the fire room has nothing to do with whether the natural ventilation shaft has been set up or not in the adjacent non-fire room. However, when a natural ventilation shaft has been set up in the fire room, it is able to effectively raise the smoke layer height.

Experimental Investigations of Fire Spread from Movable to Fixed Fire Loads in Office Fires

Experiments were conducted in a full-scale model office equipped with movable and fixed fire loads to explore the influence of ignition source location (movable fire load(s)) on fire spread. The office space was a brick structure that measured 6 m in interior length, 5 m in width, and 3.3 m in ceiling height, and was equipped with a sprinkler system that was used as a sensor, but not for suppression. The southeast corner of the room featured a 2.1 m × 0.9 m open doorway. Four fire scenarios (four different ignited movable fire configurations) were investigated experimentally. The results show that when the movable fire load is close to the fixed fire load, the fire becomes more intense. The concentrated movable fire load configuration also increases the initial fire intensity.