Development and Some Applications of Earth Tube Heat Exchanger in Gujarat

This write-up describes the development and some applications of earth tube heat exchangers in Gujarat. Work outlined here was delivered as Nanubhai Amin Memorial Lecture at Electrical Research and Development Association, Vadodara as part of Technology Day, 11 May 2004.

Cropping in Arid-Area Greenhouse

In hot, arid regions, yields are usually low and unstable. Greenhouse technology can stabilize and improve yields. But its adoption is impeded by the requirement of large amounts of water for cooling. Evaporative cooling is the most common method. Arid Area Greenhouse (AAG) is being developed for hot arid regions, particularly to reduce or eliminate the water needed for cooling. To achieve this, AAG employs earth-tube-heat-exchanger (ETHE) and static vents for environmental control. A prototype was installed in 2002 in an arid region, at village Kothara (ƒ� 23�X 14 N, ƒ� 68�X 45 E, at 21 m a.s.l.) for study. The single span saw-tooth greenhouse is 20 X 6 X 3.5 m. The ETHE is buried 3m deep directly below and coupled to it in closed-loop mode. ETHE is made of a bundle of eight mild steel pipes arranged in two tiers. Each pipe is 23 m long and 20 cm diameter. ETHE provides 20 air changes per hour. Initial cost of ETHE (material, fabrication, transport and installation) was $ 5000, nearly equal to that of greenhouse excluding instrumentation. There are three continuous closable vents - two along the base of long sides and one along the ridge. A retractable shading cover is provided over the roof. The aim was to determine (a) the extent to which ETHE and natural ventilation meet the need for environmental control and the associated costs (b) the extent to which productivity is increased, cropping season extended. By summer of 2007 five rounds of cropping have been done. ETHE was able to heat the greenhouse easily from 9�XC to 22-23�XC in half hour in the cold winter nights. Static ventilation along with shading was effective for day time control till February keeping the temperature about 34�XC inside. Subsequently, ETHE was operated. It limited the greenhouse temperature to 36-37�XC with top shaded and crop inside. If grid supply is steady it is operated for five-six hours in the day. House is closed in May-June. Yield of tomato has been close to 2 times that of the open-fields in the province. Water used was 44% of that used in open-field. The water used was mostly for plants, only a small part was for supplementary cooling using foggers. ETHE and static vents hold promise as environmental control device for greenhouses in hot arid regions. There is need to reduce installation cost by substituting plastic pipes for metal. It is also necessary to develop a more easily scalable design than the present one.

Harvesting dew to supplement drinking water supply in arid coastal villages of Gujarat

Shortage of drinking water is chronic, sever and widespread in Kutch - a hot and very arid region. It is specially acute in coastal villages where surface sources dry up rapidly and groundwater is not potable. Many of these are listed as “no source” villages and are supplied water on tanker-trucks daily from long distances. The conventional efforts to conserve and augment water resources are all in place. But one potential resource - dew - had remained unnoticed. The possibility that it may also be a supplementary resource was first noticed in the summer of 2001 when it was observed that dew condensed frequently on a plastic- clad greenhouse in Kothara, a village 15 km from the coast. That led us first, to carry out systematic measurement, and then to develop practical ways to harvest dew for human use. Measurement at Kothara was followed by measurements at two other locations along the coast - Panandhro and Mithapur. Data showed that dew occurred over an eight-month season (October- May) spanning the entire dry part of the year. Quantity was more in summer months than in winter. Dew water was found potable and safe. In the next three years development of dew harvest systems was carried out, prototypes were made and tested. After successful field trial three models were launched. The key component of the systems is the condenser, made of thin plastic film which can harvest 15 – 20 mm of dew water in the season. Condenser cools itself by radiative exchange with sky, without the use of any external energy. Working installations have been made on large roofs and on open ground. While the devices are specifically engineered to condense dew, these routinely harvest rain as well. These are being promoted as “dewrain” harvest systems that deliver useful but varying amount of water through all the months of the year.

Chiral symmetry breaking, instantons and the ultimate quenched calculation

We calculate the spectral density of the Dirac operator over an ensemble of configurations composed of overlapping instantons and anti-instantons. We find evidence that the spectral density diverges in the limit of small eigenvalues. This indicates the breaking of chiral symmetry and also provides evidence that quenched QCD may be pathological in nature.Comment: LATTICE98(confine

Disproportionate Minority Contact: Alameda County

This FOCUS explores racial and ethnic disproportion in the juvenile justice system. A case study of Alameda County, California, examines Disproportionate Minority Contact (DMC) at various points in the system and its implications. The study is juxtaposed to other societal conditions to explore patterns and potential connections