Khairul Habib

Performance Analysis of Photo Voltaic Trombe Wall for Tropical Climate

The present study examines the performance of a single zone building integrated with PV Trombe wall (PV-TW) in term of thermal load reduction and electrical energy production by varying PV Glazing types (i.e. Single Glazing, Double glazing, Double glazing filled with gas (Argon)). TRNSYS software is used for simulation in which inputs like climatic conditions, building construction details, thermal properties of materials, detail of PV-TW and orientation of building is inserted. By comparing the results of all three types of glazing it is found that PV Double glazing filled with argon shows significant reduction in mean air duct temperature, hence reduces the PV cell temperature and increases power production of PV panel. Also solar radiation captured by massive wall of PV-TW is reduced by using PV Double glazing filled with argon as compared to other types of glazing, which further reduces thermal load inside the building.

A Review of Solar Air Heater for Drying of Agricultural Products

Bulk of farm products need to be preserved because of their perishable nature. The cheapest and environmental friendly means is indirect usage of solar irradiance to reduce the moisture content of these products to a level that cannot sustain the activities of micro-organisms. The research on solar collector has gained its popularity over the years due to mans quest for green energy which has led to increase in demand for the utilization of solar energy. Harnessing of solar energy by man for drying purposes was predominantly by direct method which reduces the quality and quantity of the dried products. This work presents the most recent contributions on solar air heater of flat plate absorber category. Various models, material of component parts and performance efficiency of these air heaters were discussed and there is need for collector optimization. The study was concluded with a focus on multiple pass approach of solar harvesting.

Effect of Cryogenic Cooling on the Heat Transfer during Turning of AZ31C Magnesium Alloy

ABSTRACT A combined analytical and experimental study was carried out to analyze the effects of cryogenic cooling on temperature during turning of AZ31C magnesium alloy. Finite element method was employed to model and simulating the cryogenic and dry turning. Results obtained from the model were found to be in good agreement with the experimental observations. For the maximum temperature at the turned surface, the difference in the experimental and predicted value observed during dry and cryogenic turning was only 4 and 8% respectively. A significant reduction in the maximum temperature on the chip surface (around 35%) and tool surface (around 29%) was observed during the cryogenic turning compared to dry turning. This reduction in temperature was an attribute of liquid nitrogen, which produces intense cooling effect around the vicinity cutting zone where heat generation takes place hence enhancing the heat transfer. The isothermal region belonging to the highest temperature on the tool surface was also reduced by about 42%. The reduction in temperature during cryogenic conditions were found to be beneficial for the machining of magnesium alloys under safe conditions, reducing the risk of ignition and explosions, and also increases the sustainability of the process.

Effect of Solar Fraction on the Economic and Environmental Performance of Solar Air-Conditioning by Adsorption Chiller in a Tropical Region

Solar air-conditioning (AC) is an attractive AC system but it has intermittent output, and therefore, a conventional heater is needed as a backup. This study presents the effect of ratio of heat delivered by solar (Qsolar) to the total heat delivered to an adsorption chiller (Qsolar + Qheater) or solar fraction (SF) on the economic and environmental performance of a solar AC. This solar AC is not a solar-assisted AC, and therefore, it needs to fully cover the cooling load. The cooling demand of an office building in Kuala Lumpur, and the performance of flat-plate collectors and the adsorption chiller were calculated by equest and watsun software and by a mathematical model, respectively. Economic performance was analyzed by life-cycle cost analysis, whereas the environmental performance was analyzed by using typical emissions rate of energy systems used. It was found that a boiler was a better solution than an electric heater as a backup heater. Furthermore, the net profit (NP) at lower SF was higher because of its lower capital investment, but more emissions were released compared to the conventional AC because of the boiler operation. Thus, when economic and environmental performance were fairly considered, it is appropriate to have solar AC with an SF around 0.74.

Numerical modelling of multi-pass solar dryer filled with granite pebbles for thermal storage enhancement

In this paper, a theoretical modelling of a cheap solar thermal dryer for small and medium scale farmers with multi-pass approach has been investigated. Comsol Multiphysics modelling tool was employed using numerical technique. The rock particles were used to enhance the thermal storage of the drying system. The local weather data were used during the simulation while parameters and coefficients were sourced from literature. An improvement on efficiency of up to 7% was recorded with error of 10-5 when compared with the reported double pass solar collector. A fair distribution of hot air within the cabinets was also achieved. Though the modelling tool used was robust but the characterization of the system materials need to be done to improve the system accuracy and better prediction.

Photovoltaic-Assisted Thermoelectric Cooling and Heating Systems

At present, maintaining thermal comfort inside the buildings is becoming expensive and environmental unfriendly for a great majority of countries, as the mechanism of cooling air can prompt the tremendous utilization of energy and CO2 emissions. This chapter introduces the renewable concept of photovoltaic (PV) and thermoelectric module (TEM) implemented on the building for thermal load reduction. The chapter starts by describing the basics of the PV technology and its dependent parameters, which enhances its performance. In addition, TEMs as an alternative to conventional space conditioning technology are presented. Since PV panel can power the TEMs directly and cause no harm to the environment, therefore, the numerical modeling of PV-assisted TEMs for development of energy-efficient buildings is presented. After that, different kinds of literature focusing on the application of integration of two materials, i.e., TEM and PV for thermal load reduction of buildings, are provided. Results suggested that implementation of PV-assisted TEM system reduces 5–10 °C inlet temperature with COP ranges from 0.4 to 2.5. Lastly, the challenges and future commendation of PV-assisted TEMs technologies are discussed. Thus, it was suggested that PV-assisted TEM system provides Freon free, less energy consuming, and less CO2 emission solution to the space conditioning problem of the building as compared to traditional air-condition system.

Experimental analysis on a novel low-temperature vacuum drying with induced nucleation technique for dewatering stingless bees honey

ABSTRACT Honey spoilage is a major problem in storing stingless bee honey. A new method of honey dewatering was developed using a low-temperature vacuum drying with induced nucleation technique. The research’s objective is to investigate the performance of this method in reducing honey’s water content. Two different dewatering temperatures were applied until honey’s water content reached below 20%. The honey’s chemical compound before–after dewatering from one of the samples was tested using nuclear magnetic resonance (NMR) analysis. The dewatering rate improves significantly with higher temperature. The NMR analysis result found no changes in chemical compound before–after experiment except for ethanol.

Dynamic Modeling of Solar Air Collector with Thermal Storage Material

The investigation of solar air heater using SIMULINK tool to predict the transient state of solar thermal collector is presented in this article. The modeling is primarily centered on the solar crop drying system for small and medium scale farmers. Double transparent walls and sensible heat storage rocks were used in the modeling to aid the performance efficiency of the flat plate solar collector. The simulation was run with variable steps solver of relative tolerance of 0.001 using Dormand-Prince technique. The outcome of this investigation revealed the time trend of solar irradiance, effects of laminar forced convection on thermal coefficient, and early performance efficiency ratio. However, the model required improvement for it to accurately predict the system efficiency ratio after long period of operation.

Solar Energy Potential Estimation in Perak Using Clearness Index and Artificial Neural Network

In this paper solar energy potential has been estimated by two methods which are clearness index and artificial network (ANN) methods. The selected region is Seri Iskandar, Perak (4°24´latitude, 100°58´E longitude, 24 m altitude). Experimental data (monthly average daily radiation on horizontal surface) was obtained from UTP solar research site in UTP campus. The data include the period of 2010 to 2012 and were used for testing the artificial neural network model and also for determination of clearness index. Also the experimental data of the three meteorological, Ipoh, Bayan Lepas & KLIA were used in calculating the clearness index and for training the neural network. Result shows that clearness index for Seri Iskandar is 0.52, the highest radiation is on February (20.45 MJ/m 2 /day), annual average is 18.25 MJ/m 2 /day and clearness index is more accurate than ANN when there is limited data supply. In general, Perak states show strong potential for solar energy application.

Mathematical modelling and simulation of the dehumidifier for the tropical region of Malaysia

In this paper, mathematical model for an adiabatic dehumidifier of liquid desiccant air conditioning system is presented. Regression approach is used to generate the mathematical relation between enthalpy and humidity ratio. Flow-pattern between air & desiccant mainly affects the performance of adiabatic dehumidifier therefore to get proper dehumidification counter-flow configuration is considered as previous studies show that counter-flow direction of air to desiccant has better dehumidification results. For validation, results of present study were compared with those of numerical and analytical results of previous studies, and the agreement was found to be quite satisfactory. The developed mathematical model is then used to study the performance analyses of adiabatic-dehumidifier for the tropical region of Malaysia. Analyses are made for the week having very high range of humidity ratio (18 - 19.5 g/kg). The main concern of the current article is given on moisture removal from the ambient air according to thermal comfort-zone.