Nor Mariah Adam

ASSESSMENT OF SOLAR RADIATION ON DIVERSELY ORIENTED SURFACES AND OPTIMUM TILTS FOR SOLAR ABSORBERS IN MALAYSIAN TROPICAL LATITUDE

In this paper, the solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers were assessed. The KT solar radiation model was coded in the MATLAB-based environment to compute the monthly solar radiation values. Seven years data of monthly average daily solar radiation on a horizontal surface in Bangi, Malaysia (latitude = 3° N) was adopted as input in the simulation programme, and the results were compared with the local optimum tilt angle at solar noon and other solar radiation model. The contour mappings of solar irradiation at various orientations in 12 months were presented. Results showed that the surface tilted at ≤20° could intercept a relatively high solar intensity, which was less sensitive to the variation of azimuths with average insolation deviation of 11.82%. The monthly optimum tilt angle altered throughout the year, ranging from -24° (in equator direction) to +22° (in north direction). The estimated annual optimum slope, 1.4° facing to the equator, was close to local latitude. Based on the seasonal analysis, the north-facing surface was able to intercept higher daily average solar radiation energy compared to south-facing plane. The optimum angles for seasonal south- and north-facing surfaces were found to be 14.4° and 14.8°, respectively, with a tolerable slope deviation of ±5° from the optimal values in the present work.

Influences of Air Exchange Effectiveness and its Rate on Thermal Comfort: Naturally Ventilated Office

This article presents the effects of air exchange rate (ACH) and air exchange effectiveness (AEE) on thermal comfort level of a naturally ventilated office room. The study was conducted in an office at UPM, Malaysia. Influence of ACH and AEE on thermal comfort has not been investigated and is, therefore, not well understood. The main objective of this research is to investigate and assess these influences through the variable windows-door opening arrangements. To determine the windows-door opening performance in terms of ventilation air flow rate, 14 opening configurations have been considered. Thermal comfort variables were measured at the same time when ACH and AEE were evaluated. Through these data, the thermal comfort Fangers indices (Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD)), ACH and AEE were calculated. These results showed that for a naturally ventilated office room three linear regression equations of PMV versus ACH and three linear regression equations of PMV versus AEE can be derived.

Perception of Thermal Comfort in the Enclosed Transitional Space of Tropical Buildings

The enclosed lift lobby distinguishes itself as a unique form of region categorised under building transitional spaces. This paper reports on an evaluation of thermal comfort conditions in a prominent transitional space in buildings which is the enclosed lift lobby of an educational institution in Malaysia, using field survey which included objective measurement and subjective assessment. The temperature set-point of air conditioner was increased and maintained at 26°C to investigate the human thermal perceptions in the enclosed region. Comparison was made on the percentage of thermal sensation, preference, acceptability and general comfort votes obtained from field survey. The outcomes clearly indicated that the human thermal perception in the enclosed lift lobby would be directly proportional to the level of human occupancy, and any sudden temperature change could lead to thermal discomfort of occupants. The respondents generally preferred to have cooler environment, rather than warmer one. Also, comfortable temperature can be obtained even with higher air conditioner thermostat settings. These findings may serve as a guide for building operators in the tropics to control the energy consumption of cooling equipment attached to the enclosed transitional spaces.

Thermal comfort of an air-conditioned office through different windows-door opening arrangements

This paper investigates the thermal comfort level of an office room through various windows-door opening arrangements in hot and humid climate. To determine the windows-door opening performance, 14 opening configurations have been considered and the combination of opening arrangements was carried out in an air-conditioned office at UPM, Malaysia. After conducting objective measurement for each condition, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) were calculated. The concentrations of carbon dioxide (CO2) were also monitored. Subjective survey involved questions on the thermal environmental perception and indoor air quality for office occupants for this study. Objective data analysis showed that in most of conditions office had thermal conditions falling within the comfort zone of ASHRAE standard 55, and in all of conditions neutral temperatures are higher than ASHRAE standard requirements. Subjective results revealed that staff has higher thermal comfort level as compared to what PMV has predicted. Practical application: It is believed that the results in this paper will contribute to knowledge that international standards are not applicable in hot and humid climate. Fanger equations would give the results for European conditions, people in hot- humid climate have some cultural preferences that are different from the Europeans hence modifying these equations and standards for this climate are necessary. In terms of the use of climatic control to modify the indoor environment it is found that when the occupants have the freedom to modify the environment, and make necessary adjustment, they always use windows-door opening arrangements to compensate for the less comfortable thermal condition and increase air movement.

Prediction of the thermal performance of solar air heaters by Internet-based mathematical simulation

Abstract This paper presents an internet-based mathematical simulation for predicting the thermal performance of solar air collectors to collect energy used for drying various products. The solution procedure was performed for a flat plate collector and a V-groove absorber. The thermal performance was determined over a wide range of operating conditions, but in the same configuration for the two types of solar collector. The V-groove absorber was found to be more efficient than the flat plate collector. The optimum operating conditions were determined. Comparison between predicted and experimental results indicates that the proposed mathematical model can be used for estimating the thermal performance of solar air heaters with reasonable accuracy.

A technique to capture multi-disciplinary tacit knowledge during the conceptual design phase of a building project

The construction industry is suffering from incomplete knowledge flow that results in time and cost over-runs. Many researchers believe that a large part of this problem is related to the design phase being a tacit knowledge-dominated area. Since tacitness of knowledge contributes to incomplete flow of knowledge, we posit that facilitating the conversion of tacit knowledge to explicit knowledge can improve the overall knowledge flow. Within this context, this paper analyses recognised knowledge-capturing techniques and compares them in view of the operating characteristics of the conceptual design phase. This paper proposes a new tacit knowledge-capturing technique for this phase. The outcomes include a new knowledge-capturing technique, a method for validation of the proposed technique, and recommendations on how to deal with the challenges concomitant with the application and utilisation of the proposed technique in the building industry. By proposing a combinational tacit knowledge-capturing technique, this study attempts to mitigate the impact of the potential incomplete knowledge flow during the conceptual design phase in building projects.

Evaluation of indoor thermal environment in a radiant-cooled-floor office building in Malaysia

This paper presents the findings of a thermal comfort survey conducted in a tropical green office building. The building was installed with a slab-integrated radiant cooling system, which operated concurrently with an integrated variable-air-volume system. Evaluation of indoor thermal environment was made, where both objective and subjective assessments were carried out. The air temperature, air velocity, relative humidity and surface temperatures were measured by using calibrated sensors. Based on the data collected from the field assessment, the thermal comforts indices with expectancy factor were calculated. The results showed that thermal comfort parameters were within the comfort range specified in a local guideline, except for the air velocity profile. Besides, discrepancy between the Predicted Mean Vote (PMV) with expectancy factor and Actual Mean Vote (AMV) was found, which showed that the former still overestimated the thermal sensation of occupants although an expectancy factor of 0.5 was used.

Calibration and Accuracy Determination of a Microwave Type Sensor for Measuring Grain Flow

Impact type grain flow sensor for crop yield monitoring is known to have problem of some thrown grain by the elevator conveyor in a combine not hitting the sensing impact plate. New technology of microwave solid flow sensor was used to solve the problem of impact-type sensor. A calibration stand with its instrumentation systems to stimulate the actual operation of the clean grain auger in a rice combine had been designed and constructed in this study for the purpose of conducting the calibration and evaluation study of the sensor. Two different solid flow sensor orientations and three different solid flow sensor extrusions were investigated in order to find the best positioning of the sensor on the chute for the measurement. Results from the conducted tests indicates that the best sensor positioning is on totally flat ground at 180o orientation and 8 cm extrusion of the chute cross section (R2=0.9400). Then, the solid flow sensor was tested at seven chute pitch angle positions (i.e-4.5o, -3.0o, -1.5o, 0o, +1.5o, + 3.0o, and +4.5 o), seven chute roll angle positions (i.e-4.5o,-3.0o, -1.5 o, 0o, +1.5o, +3.0 o, and +4.5o). Finally, accuracy tests undertaken to compare the real time measurements against the average flow measurements. ANOVA test shows that both pitch angle and roll angle positions have significant effects on the measurement accuracy of the sensor. The measurement errors increased with increasing roll angles and increasing pitch angle. Conclusively, this conducted laboratory study was able to quantify the measurement accuracy of the SWR Solid Flow sensor for real-time measurement of grain flow under a simulated laboratory rice combine test set-up.

Investigation on alternative methods to enhance the cooling capacity of an open pool reactor

It is a common phenomenon for any research reactor with less than 1MWth to have very limited applications. Thus, many of such reactors have undertaken upgrading exercises to increase its capacity. Most of the research reactor which have undergone power or flux upgrading, increased the cooling performance through the installation of higher capacity heat removal system along with forced convection mechanism inside the pool. This approach would require higher cost as well as major modification of the reactor pool. Other alternatives which require less modification and cost have been investigated using computed fluid dynamic simulation. This study has shown that the installation of in-pool pumps and conduction rods inside the existing pool system have promising potential to enhance the heat removal capacity of a natural convection cooling system.

Preventive Maintenance Scheduling Sequence for Bottleneck Equipment in a Manufacturing Line

This paper analyzes preventive maintenance scheduling of bottleneck equipment in a line concept of a wafer manufacturing line that has buffer in between equipment. After the start-up of the manufacturing, it has implemented time based maintenance and counter based maintenance without any fix sequence. The maintenance team will select in advance the date and time of the actual preventive maintenance to be perform and making sure all resources are planned. Then maintenance team implemented a Preventive Maintenance sequence which gives the lowest impact in production loss without sacrificing equipment’s quality and safety. This Preventive Maintenance Scheduling sequence is the best suitable method for manufacturing equipment that has buffer in between equipment which is arranged in a line concept. It has also been tested and proven in a wafer manufacturing industry.