No description available.

In the spring, apple orchards are susceptible to freeze damage. Various approaches to orchard protection have been used in the past. Overhead sprinkling for bloom delay has been effective in extending to a later period in the spring the freeze hardiness of apple buds. Thus, protection against a late spring freeze is obtained. Previous research has not been conducted to determine optimum sprinkling times in the spring, the most effective threshold temperature, the amount of water needed to provide adequate bud protection, and the daily length of sprinkling time. A 2-year investigation was conducted with the objective of obtaining basic information to help in system design and the operational aspects of overhead sprinkling. The experiment was designed to determine the effectiveness of a system sprinkling beginning at the end of rest and at Celsius growing degree hour accumulations relating to stages bud development. The evaluation of limited and unlimited water use and the relation to bloom delay was obtained. The two sprinkler types studied were umbrella and impact. On the umbrella sprinklers, four cycling times (1/2, 1/3, 1/4, and 1/6 time) and three threshold temperatures (7, 10, and 13 C) were tested. On the impact sprinkler, three nozzle sizes (4.0, 3.6, and 2.8 mm) were evaluated. The investigation answered many questions, the most important of which were: (1) when only limited bloom delay is needed, more freeze protection can be obtained by sprinkling in the early spring than in the late spring; (2) bloom delay can be regulated by terminating sprinkling at different stages of bud development; (3) to obtain maximum delay, sprinkling should begin at the end of rest and a low threshold temperature for sprinkling should be used for sprinkler initiation; (4) when limited delay is required, greater efficiency of water use can be obtained by lowering the threshold temperature and lowering the application rate.

Green roofs have become an important urban mitigation technology due to their ability to address multiple environmental issues. One of the most common benefits attributed to green roofs is the reduction in heating and cooling loads in buildings by dissipating heat through evaporation. This study focuses on evaluating the effect that evaporative cooling has on the thermal performance of green roofs. Sponge and floral foam were used as porous media for their ability to retain water inside its body, transport it to the surface, evaporate it at a constant rate and for their different pore sizes. Test trays containing sponge or floral foam saturated with water were tested in a low speed wind tunnel equipped to measure weight, temperature and heat flux. Two types of experiments were conducted: one with evaporation at the surface, and the other with evaporation blocked by an impervious layer. The testing conditions for all tests were kept constant except for the ability of evaporation to happen. Evaporation rate for floral foam was 0.14 kg/m2hr and 0.29 kg/m2hr for sponge. Results of tests with evaporation show a decrease of 45-49% in heat conducted through the roof when compared to the tests without evaporation. For optimal thermal performance of green roofs, a material that enhances water transport and thus evaporation at the surface is necessary with large pores and low field capacity. Surface temperatures on test with evaporation were found to be between 3-7°C lower than those without evaporation. Applying a 2 sample t-test to the data, the relationship between heat flux and evaporation was found to be statistically significant.

This study focuses on how green roof thermal performance is affected by the soil moisture in summer condition. It aims to determine whether moist soil is a better insulator during the summer months than dry soil. A soil model is developed to predict simultaneous conduction, convection, and surface evaporation for a layer of moist soil representing a green roof. It used to analyze evaporation process and its affect on the soil resistance. The model considers only bare soil without vegetation on the roof. The model predicts the soil surface temperature as it is affected by soil moisture content, which can then be used to calculate heat transfer through the soil layer. An experimental dry out test was conducted to measure the soil moisture and soil temperature histories. Comparison of the predicted and measured sol surface temperature shows that the model reasonably captures the actual behavior. The evaporative cooling effectively reduces the soil surface temperature and heat flux in moist soil and can be used as an effective way to insulate the roof.

Thesis. 1976. M.S. cn--Massachusetts Institute of Technology. Dept. of Nuclear Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / M.S.cn

The PhD thesis deals with the theoretical evaluation of the potential use of night cooling techniques in condition of the Czech Republic. Mainly aims to evaluate the potential of night cooling, which uses the physical phenomenon of radiation against the night sky. This technique is widely used mainly in the dry and hot regions where there are the most suitable climatic conditions for this cooling method. The work is based on the current state of knowledge in the area of passive and low-energy cooling systems. These knowledges are applied to the conditions of Czech Republic and by using simulations of the energy, behaviour of the buildings explores the benefits in terms of improving of the internal microclimate and from the perspective of economy operation of conventional cooling equipment. In order to establish the benefits of night cooling on the operation of the building in the dynamically changing conditions, the modular simulation program TRNSYS was used, which is suitable for the analysis of energy systems of buildings and their behaviour. The results of simulation results were converted to thermal comfort parameters of the PMV and the PPD.

Farmers are limited in the amount of specialty crops they can plant, harvest and market without adequate cooling to preserve commodities before sale. A cooler available at a farm would allow the farmer to harvest his produce earlier and take it to market at a later time. Cooling available on the farm will help a farmer to harvest commodities during peak harvest times and store it for future sale at multiple farmers markets or over a period of a week or more at a farm market. A cooler will give a farmer more logistical options. An indirect-direct evaporative pad cooling can provide cooling with high humidity which is sufficient to prolong shelf life. A cool room with window air conditioning (AC) was modified by adding indirect-direct evaporative cooling. The cool room was used for comparative study of produce shelf life under AC (with CoolBot), indirect-direct evaporative cooling (EC), residential AC (RES), and farm building (FB) storage. Results showed that FB had a lower shelf life because of non-conditioned space. RES was a table in an office building with a temperature of about 22°C. For produce with medium temperature requirements such as tomato, cucumber, and green pepper the shelf life was prolonged more in the cooler room. Strawberry and blueberry had a much longer shelf life in a cooler. The shelf life of the blueberry stored at Cooler AC was longer about two and a half fold longer than Cooler EC and RES, and five and half fold longer than FB. The shelf life of the strawberry in Cooler AC was longer one-fold than Cooler EC, two and a half fold longer than RES, and five-fold longer than FB. The shelf life of green pepper stored in Cooler AC was longer fivefold than Cooler EC and nine and a half fold longer than RES and FB. The shelf life of cucumber stored at Cooler AC was longer two fold than Cooler EC and 3.3-fold longer than RES and four fold longer than FB. The shelf life of tomato stored at Cooler AC was longer 1.25-fold than Cooler EC, 1.75 fold longer than RES and two and a half fold longer than FB. Generally stored fruits and vegetables in Cooler AC was maintained quality with minimal weight loss that allows a farmer to store their produce while maintaining shelf life. Cooler EC can be used to store produce for a shorter time with higher weight loss. Finally, FB had a shorter shelf life due to the non-conditioned space.

No description available.

In this thesis, I demonstrate Doppler and Sisyphus cooling of a cryogenic buffer-gas beam of CaH molecules. I detail the construction and optimization of the experimental apparatus, including the cryogenic source, laser systems, vacuum systems and detection schemes. I demonstrate that the cryogenic source produces a bright and slow beam of CaH molecules via ablation of a solid chemical target and thermalization with a He buffer gas. The molecular beam exits the ablation cell with an average forward velocity of 250 ±200 m/s and a molecular beam flux per ablation pulse of ≈ 1×1010 per steradian per pulse. I present the spectroscopic determination of the molecular transitions necessary to pursue laser cooling. These include the X2Σ+ → A2Π1/2 and the X2Σ+ → B2Σ+ transitions that each contain two spin-rotation states, J = 1/2 and J = 3/2, and a further pair of hyperfine states, F = 0,1 and F = 1,2, respectively. Finally, I describe the vibrational repumping transitions between the four hyperfine states of the J = 1/2 and J = 3/2 branches of the V = 1 vibrational state back to the ground state via decay from an intermediary state, X2Σ+(V = 1) → B2Σ+(V = 0) → X2Σ+(V = 0). I present measurements of the vibrational decay probabilities from the B2Σ+(V = 0) and A2Π1/2(V = 0) excited states to the V = 0,1 and 2 states of the ground X2Σ+ state. Next, I show that we can achieve a high scattering rate of ≈ 1.6E6 photons/second while cycling on the X2Σ+ → A2Π1/2 transition. Finally, I demonstrate the ability to perform transverse cooling of a beam of CaH molecules through both the Doppler mechanism and magnetically assisted Sisyphus mechanism. With the help of a transverse standing wave of laser light, I show that we are able to lower the molecular beam’s transverse temperature from 12.2±1.2 mK to 5.7±1.1mK. This thesis represents a promising start to laser slowing and magneto-optical trapping of CaH molecules, which could provide trapped ultracold samples of atomic hydrogen upon dissociation of the trapped CaH molecules.

In recent decades, greater interest in the effect of rotational wakes on gas turbine film cooling applications has produced increasing numbers of studies on these unsteady phenomena. Wakes are primarily shed from upstream components such as transition duct walls, stator vanes, and rotors. Studies have shown that in areas of unsteady flow, the best performing parameters in conventional steady investigations may not be the best for unsteady applications. One common method of modeling the unsteady wake interaction in subsonic flows is the use of spoke wheel type wake generators using cylindrical rods to produce the velocity detriment and local increase in turbulence intensity. Though the impact of wakes have been studied for decades on airfoil losses and boundary layer transition, only recently has the film cooling and wake interaction been investigated. The existing work is primarily on leading edge models and airfoil cascades. The primary parameter characterizing the unsteady wakes is the dimensionless or reduced frequency known as the Strouhal number. The film cooling jet itself has dominant frequencies resulting from the shear and the jet trailing wake shedding, depending on the injectant flow rate. There exist great deficiencies in the fundamental understanding of the interaction of these two frequencies. Heat transfer considerations are also relatively recent being studied only since the early 1990's. Heat transfer coefficients and film cooling effectiveness have been reported for leading edge and linear airfoil cascades. In the case of the linear cascade, no data can be taken near the endwall region due to the varying tangential velocity of wake generating rod. The current work expands on this initiative incorporating a sector annular duct as the test setting for the rotating wakes focusing on this endwall region.; Studies in to the effect of the rods in this alternate orientation include film cooling effectiveness using temperature sensitive paint, impact of wake rod to film cooling hole diameter ratio, and time accurate numerical predictions and comparisons with experimental work. Data are shown for a range of momentum flux ratios and Strouhal numbers. The result of this work sets the stage for the complete understanding of the unsteady wake and inclined jet interaction.