Sudden changes in crop environment, as influenced by total solar eclipse

The Division of Agricultural Meteorology, at Pune of IMD conducted an experiment at Principal Evapotranspiration Observatory, Canning, W.B., during October, 1995 to study the sudden changes in crop environment. The present study revealed that both the crop canopy temperature and observatory temperature at different heights recorded sharp fall of around 2.0°C at 0900 hr (IST) on the eclipse day. The relative humidity (% ) increased sharply at 0900 hr (IST) on the eclipse day within crop canopy as well as within observatory. The soil temperature dropped suddenly at 10 and 20 cm depths of the subsoil and delayed reversal of the soil temperature gradient occurred on the eclipse day; the grass minimum temperature was 21.2°C. Bright sunshine hours reduced by 0.8 on 'the eclipse day as compared to the preceding and succeeding days. The wind during the eclipse period was almost calm between 0900 -0930 hr (IST). The daily total ET recorded on the eclipse day was the minimum. The rate of evapotranspiration was less than half as compared to the other days, as recorded at 0830 hr (IST) (0.2 mm) on the eclipse day, which was closely followed by that observed at 1130 hr (IST) (0.3 mm).

The Ability of a Soil Temperature Gradient-Based Methodology to Detect Leaks from Pipelines in Buried District Heating Channels

We carried out several numerical experiments to analyze how different boundary conditions affect the ability to detect small pipeline leaks. Our method is based on determining the soil temperature gradient above a buried district heating channel. The equivalent thermal conductivity of a wet insulation (λeq) value of 0.5 W/(m·K) was used to mimic a small water leakage. To evaluate the heat loss through the channel cross section, the heat conduction model was used for the pipe insulation, the concrete, and the soil, while the convection model was considered within the channel. The following effects were used to simulate different operating conditions: heat convection at the soil surface, leakage only from the supply or return pipe, soil height above the channel, soil thermal conductivity, and pipe diameter. With the exception of leakage only from the return pipe and low soil thermal conductivity 0.4 W/(m·K), the results showed a doubling of the soil temperature gradient when compared with the no-leakage case. This fact undoubtedly confirms the potential of the method, which is particularly suitable for leak detection in old pipelines that have priority for renovation. A key added value of this research is that the soil temperature gradient-based leak detection technique was found useful in most foreseeable DH operating situations.

A Numerical Model to Estimate the Soil Thermal Conductivity Using Field Experimental Data

Soil thermal conductivity is an important parameter for understanding soil heat transfer. It is difficult to measure in situ with available instruments. This work aims to propose a numerical model to estimate the thermal conductivity from the experimental measurements of soil heat flux and soil temperature. The new numerical model is based on the Fourier Law adding a constant empirical parameter to minimize the uncertainties contained in the data from field experiments. Numerically, the soil thermal conductivity is obtained by experimental linear data fitting by the Least Squares Method (LSM). This method avoids numerical indetermination when the soil temperature gradient or soil heat flux is very close to zero. The new model is tested against the different numerical methodology to estimate the soil heat flux and validated with field experimental data. The results indicate that the proposed model represents the experimental data satisfactorily. In addition, we show the influence of the different methodologies on evaluating the dependence of the thermal conductivity on the soil water content.