Rizwan Ahmed Memon

Impacts of environmental factors on urban heating.

This study investigated the impact of important environmental variables (i.e., wind speed, solar radiation and cloud cover) on urban heating. Meteorological parameters for fifteen years (from 1990 to 2005), collected at a well developed and densely populated commercial area (Tsim Sha Tsui, Hong Kong), were analyzed in details. Urban heat island intensity (UHII), a well known indicator of urban heating, has been determined as the spatially averaged air-temperature difference between Tsim Sha Tsui and Ta Kwu Ling (a thinly populated rural area with lush vegetation). Results showed that the UHII and cloud cover have increased by around 9.3% and 4%, respectively, whereas the wind speed and solar radiation have decreased by around 24% and 8.5%, respectively. The month of December experienced the highest UHII (10.2 degrees C) but the lowest wind speed (2.6 m/sec) and cloud cover (3.8 oktas). Conversely, the month of April observed the highest increases in the UHII (over 100%) and the highest decreases in wind speed (over 40%) over fifteen years. Notably, the increases in the UHII and reductions in the wind speed were the highest during the night-time and early morning. Conversely, the intensity of solar radiation reduced while the intensity of urban cool island (UCII) increased during solar noon-time. Results demonstrated strong negative correlation between the UHII and wind speed (coefficient of determination, R2 = 0.8) but no negative correlation between UCII and solar radiation attenuation. A possible negative correlation between UHII and cloud cover was investigated but could not be substantiated.

Parametric study of condensation at heating, ventilation, and air-conditioning duct's external surface:

The compression of insulation causes around a heating, ventilation, and air-conditioning duct usually resulted in dew formation around the outer surfaces because of low temperature, which causes significant energy and financial losses. The parameters such as supply air flow rate, supply air temperature, ambient air speed, and the convective heat transfer coefficient (ho) plays significant role in dew formation. In this paper, the parametric study is performed to investigate the effects of these parameters on the external surface temperature of the duct to avoid condensation. A mathematical model is developed to quantify these effects using preliminary data obtained from the heating, ventilation, and air-conditioning system of a pharmaceutical company. The results reveal that external surface temperature increases with an increase in insulation thickness and supply air temperature, whereas it decreases with higher supply air flow rate. It is estimated that the minimum insulation thickness at joint and bend should be maintained between 15–55 and 15–35 mm, respectively, with a variation in ho between 6 and 22 W/m2K to avoid condensation. Additionally, it is estimated that air flow rate should be greater than 1.4 m3/s at 10 W/m2 K and 2.2 m3/s at 22 W/m2 K. Similarly, the ambient air speed should be greater than 2.8 m/s at 6 W/m2 K, respectively. Practical application: Building services engineers have a paucity of information on the effects of the compression of heating, ventilation, and air-conditioning duct thermal insulation. It can cause condensation that will adversely affect the insulation material, thereby increasing the maintenance cost as well increasing the heat loss from the duct so affecting the conditions of supply air. Proper insulation thickness and operating parameters are important for building owners and operators to control ongoing expenses of buildings. This paper seeks to quantify the effect of insulation compression to improve understanding so that this important area may be properly considered by the building services engineer.

Energy Savings and CO2 Reduction through Solar Water Heater Technology in Sindh Pakistan

Pakistan suffers worst energy crises due to unavailability of primary energy sources. One of the solutions to energy problems of Pakistan lies in utilization of renewable energy sources like solar energy. One of the possible uses of solar energy is in the form of water eating. This work explored the availability of solar energy in the Sindh province of Pakistan. Moreover potential fuel savings and reduction in CO2 emission due to the use of solar water heating system is also evaluated. The RETScreen software was used for evaluation of fuel savings and CO2 emission reduction from a solar water heating system. Results show that the annual natural gas supplied to an average household in the three main cities of Sindh i.e., Karachi, Hyderabad and Sukkur could be reduced by 513.5, 409 and 543.5 m3, respectively. Annual reductions in emissions of CO2 for Karachi, Hyderabad and Sukkur were estimated to be 1, 0.8 and 1 tCO2 respectively. It is concluded that the utilization of solar energy for water heating in domestic sector of Sindh Pakistan could save fuel fossil and reduce environmental pollutants that in-turn may help mitigate energy crises in the country.