Shine Hours Research Articles

Effect of water depth on internal heat and mass transfer for active solar distillation

In this communication, an attempt has been made to find out the convective heat transfer coefficient for active solar distillation system. It is a well-known fact that the distillate output (the yield) decreases significantly with the increase of water depth in the basin of the solar still. It is also known that more yield is obtained in case of active solar distillation system as compared to passive solar still due to higher temperature difference between the water and inner glass cover temperatures in the active mode. For the present study, experiments have been conducted for 24 hours during winter months for different water depths in the basin (0.05, 0.1 and 0.15 m) for passive as well as active solar distillation system. The objective of the present paper is to study the effect of different water depths in the basin on the heat and mass transfer coefficients. It is inferred that the convective heat transfer coefficient between water and inner condensing cover depends significantly on the water depth in the basin. It is also observed that more yield is obtained during the off shine hours as compared to daytime for higher water depths in solar still (0.10 m and 0.15 m) due to storage effect.

Influence of weed management practices on weed dynamics and yield of urdbean (Vigna mungo) under rainfed conditions of Jammu

Experiments were conducted during kharif 2007 and 2009 in Inceptisols, to study the effect of different pre (PE) and post-emergence (POE) herbicides along with two hand weedings (HW) at 20 and 40 days after sowing (DAS) and weedy check on urdbean {Vigna mungo (L.) Hepper}. Highest seed yield was observed with two HWs at 20 and 40 DAS and the values were found statistically at par with POE application of imazethapyr 25 g/ha at 20 DAS. The highest weed control efficiency and lowest weed biomass was recorded with two HWs at 20 and 40 DAS fol- lowed by application of imazethapyr 25 g/ha (post-emergence) at 20 DAS. Application of Fenoxaprop-p-ethyl, quizalofop-p-ethyl, chlorimuron-p-ethyl as post-emergence and their combinations also reduced weed biomass and improved seed yield and yield attributing parameters as compared to weedy check. Treatment weedy check registered the highest values of weed count and weeds biomass and lowest seed yield and yield attributing char- acters in both the years of study. Rainfall was directly related to weed count and weed dry matter accumulation with the coefficient of 0.65 and 0.61, respectively. Weed dry matter accumulation was directly related with sun- shine hours with an accuracy of 67%, whereas, weed count was lesser related with sunshine hours of the day with an accuracy of 34%. Grain and biological yield of urdbean crop decreased at the rate of 3.3 and 7.5 kg/ha under weedy check with an accuracy of 88 and 73%, respectively.

Further data on solar radiation in Shiraz, Iran

Instantaneous solar radiation data read from the chart of global solar radiation on a horizontal surface as well as sun shine hours in Shiraz during the 1991–1993 period are analysed and compared with solar conditions in the 1970s and 80s. It is apparent from the recorded data and the consequent analysis of the statistics that, while the city of Shiraz possesses a relatively high abundance of sunshine with clear sky index conditions, there is a gradual decay in the values of instantaneous solar radiation and its maximum.

A novel underground solar water heater

This communication presents the performance of a novel solar water heater which consists of a rectangular tank (110 × 80 × 10 cm) made up of G.I. sheet and is provided with inlet and outlet pipes. The tank is buried underground; the top surface of the ground is blackened and glazed so that the surface acts as an absorber of solar radiation while the tank as well as the sorrounding earth serves as the storage system. During off-sun shine hours the top surface is covered by a layer of insulation so as to prevent upward loss. An analytical model has been presented to predict the performance of such a system.

Aphid incidence and its correlation with different environmental factors

The aphid incidence and its correlation with environmental factors were studied. Mustard variety "Sampad" was used as test crop. Aphid incidence varied significantly at various parts of mustard plant and time of the day. The highest number of aphid was observed in the vegetative parts of the mustard plant in the morning. High cloudiness, relative humidity and dew point favoured the aphid population and slight rain fall quickly declined the aphid population. Among the different environmental factors maximum temperature, dew point and sun shine hours were positively correlated with aphid population and minimum temperature, relative humidity and wind speed were negatively correlated with aphid population. Keywords: Mustard aphid; Incidence; Environmental factors DOI: 10.3329/jbau.v7i1.4791 J. Bangladesh Agril. Univ. 7(1): 15-18, 2009