The Marnoch heat engine (MHE) is a new type of power generation device that is under research and development at the University of Ontario Institute of Technology. In this thesis, the transient heat transfer behaviour of the source heat exchanger of the Marnoch heat engine is studied, and its operation for laminar and turbulent flows is modelled. The temperature variations of the working fluid, the heating fluid and the wall, are calculated. The temperature distribution of the fluids and the wall over the length of the heat exchanger is also calculated. It is found that the temperature of the working fluid rises sharply to a peak and then gradually decreases. The wall temperature decreases exponentially, and the temperature of the heating fluid falls sharply, and then gradually decreases. A base model for the step change in the mass flow of the working fluid is developed and compared against past works for the purpose of validation. / UOIT

<p>Run-around energy recovery systems are one of the several ways for transferring energy between two air streams. Compared with other air-to-air energy recovery systems, run-around systems are very reliable and flexible, especially in retro-fit applications. Previous research in this area has mainly dealt with sensible run-around heat recovery system. However, an ideal air-to-air energy recovery device should be able to recover moisture as well as sensible heat. It is the objective of this research project to simulate a run-around system that exchanges both moisture and sensible heat, and to do a performance analysis to find the design characteristics of such a system.</p><p>The first step in the study was to develop a numerical model for a run-around system with two sensible heat exchangers and validate the model using data from the published literature. Following this, a mathematical/numerical model of a heat and moisture exchanger and the run-around heat and moisture recovery system was developed using only basic physical and chemical principles, component properties and operating conditions. With this model, the position dependent temperature and moisture content properties of both a single exchanger and a run-around system were simulated for steady state operating conditions. This simulation enables the study of the performance of the exchanger and the run-around system. In the investigation, the method was employed to characterize the performance of a single exchanger and a run-around system and two new independent parameters, the number of mass transfer units and mass flow rate ratio, were introduced.</p><p>The results show that, for the sensible run-around heat recovery system with a specified NTU, the maximum effectiveness occurs approximately at a heat capacity ratio, but for the run-around system with both heat and moisture exchange, the maximum effectiveness occurs approximately at heat capacity ratio for ARI summer and winter test conditions and the maximum effectiveness varies with . The analysis of the run-around system with both heat and moisture exchange with and as independent parameters shows that the maximum effectiveness occurs approximately when . As well, the value of maximum effectiveness was found to be different when different coupling salt solutions were used.

University of Macau / Faculty of Science and Technology / Department of Electromechanical Engineering

An agroclimatic risk assessment for agricultural production across the Canadian prairie provinces has been assembled to address challenges related to frost, heat units, and moisture. Based on 30 years of daily climate data from 1971 though 2000 from 230 climate stations, the assessment provides a series of risk maps depicting the likelihood to achieve certain thresholds of frost dates or durations, heat unit accumulations, growing season rainfall, crop water demand (CWD), and crop water deficits. Maps for each parameter provide a spatial representation of 50%, 25%, and 10% risks and the coefficient of variation. / October 2007

<p>Run-around energy recovery systems are one of the several ways for transferring energy between two air streams. Compared with other air-to-air energy recovery systems, run-around systems are very reliable and flexible, especially in retro-fit applications. Previous research in this area has mainly dealt with sensible run-around heat recovery system. However, an ideal air-to-air energy recovery device should be able to recover moisture as well as sensible heat. It is the objective of this research project to simulate a run-around system that exchanges both moisture and sensible heat, and to do a performance analysis to find the design characteristics of such a system.</p><p>The first step in the study was to develop a numerical model for a run-around system with two sensible heat exchangers and validate the model using data from the published literature. Following this, a mathematical/numerical model of a heat and moisture exchanger and the run-around heat and moisture recovery system was developed using only basic physical and chemical principles, component properties and operating conditions. With this model, the position dependent temperature and moisture content properties of both a single exchanger and a run-around system were simulated for steady state operating conditions. This simulation enables the study of the performance of the exchanger and the run-around system. In the investigation, the method was employed to characterize the performance of a single exchanger and a run-around system and two new independent parameters, the number of mass transfer units and mass flow rate ratio, were introduced.</p><p>The results show that, for the sensible run-around heat recovery system with a specified NTU, the maximum effectiveness occurs approximately at a heat capacity ratio, but for the run-around system with both heat and moisture exchange, the maximum effectiveness occurs approximately at heat capacity ratio for ARI summer and winter test conditions and the maximum effectiveness varies with . The analysis of the run-around system with both heat and moisture exchange with and as independent parameters shows that the maximum effectiveness occurs approximately when . As well, the value of maximum effectiveness was found to be different when different coupling salt solutions were used.

Four studies were conducted in the Texas Panhandle during the summer of 2007 to evaluate methods for cooling cattle in three phases of production (unweaned calves in hutches, weaned heifers on pasture and lactating cows). Unweaned calves (n = 20) housed in polyethylene hutches, covered with reflective aluminum and bubble film insulation, were compared to calves (n = 18) in similar, un-insulated hutches. Mean thermal heat index (THI) for the trial was 71.9 ± 5.5 (SD). Insulation treatment did not affect body weight gain (P > 0.044). Insulation affected interior hutch temperature, calf body temperature, and respiration rate (P < 0.05), indicating insulation may moderate temperature extremes within the hutch. Weaned heifers (n = 55) on pastures with shade were compared to similar heifers (n = 62) in pastures without shade. Mean THI for the trials was 70.8 ± 6.2 (SD). Shade treatment increased body temperature (P = 0.03) and decreased body weight gain. The effect of shade on foraging behavior was dependant on THI. Shade use by heifers was dependant on THI and wind speed. Heifers utilized shade when THI was above 72, especially when wind speed was low. Feed bunk attendance was compared among pens (n = 3) of lactating cows where the feed bunk was equipped with water sprinklers that sprayed the backs of cows and pens (n = 2) without feed bunk sprinklers. Mean THI for the trial was 70.8 ± 5.7 (SD). Feed bunk sprinklers mediated the affect of elevated THI on decreasing bunk attendance, but overall bunk attendance was not different among treatments. Lactating dairy cows, cooled with water sprinklers and fans three times each day in the holding pen prior to milking, were compared with similar cows cooled in the holding pen by fans only. Mean THI for the trial was 69.9 ± 5.3 (SD). Body temperature, milk yield and somatic cell count were not different among treatments. Sprinkled cows had lower milk fat and total protein than control cows. Sprinkling cows in the holding pen when THI is less than 70 may negatively affect milk production.

Experiments and numerical predictions were conducted to study heat (mass) transfer characteristics in a two-pass trapezoidal channel simulating the cooling passage of a gas turbine blade. Three different rib configurations were tested for the air entering the smaller cross section of the trapezoidal channel as well as the larger cross section of the trapezoidal channel at four different Reynolds numbers of 9,400, 16,800, 31,800, and 57,200. (+) 60º ribs, (–) 60º ribs and 60º V-shaped ribs were attached on both the top and bottom walls in parallel sequence. A naphthalene sublimation technique was used, and the heat and mass transfer analogy was applied to convert the mass transfer coefficients to heat transfer coefficients. Numerical predictions of three-dimensional flow and heat transfer also were performed for the trapezoidal channel with and without 90º ribs tested by Lee et al. (2007). Reynolds stress turbulence model (RSM) in the FLUENT CFD code was used to calculate the heat transfer coefficients and flow fields at Re = 31,800. The results showed that the combined effects of the rib angle, rib orientation, and the sharp 180° turn significantly affected the heat (mass) transfer distributions. The secondary flows induced by the sharp 180° turn and the angled or V-shaped ribs played a very prominent role in heat (mass) transfer enhancements. The heat (mass) transfer enhancements and the pressure drops across the turn for 60° V-shaped ribs had the highest values, then came the case of (+) 60° ribs, and the heat (mass) transfer enhancements and the friction factor ratios for (–) 60º ribs was the lowest. However, comparing (–) 60º ribs with the 90º ribs, (–) 60º ribs produced higher heat (mass) transfer enhancements than the 90º ribs, as results of the secondary flow induced by the (–) 60º ribs. The overall average heat (mass) transfer for the larger inlet cases was always higher than that for the smaller inlet cases in the ribbed trapezoidal channel. Considering the thermal performance comparisons of the (+) 60° ribs, the (–) 60º ribs, and 60° V-shaped ribs for the smaller inlet cases, the highest thermal performance was produced by the (–) 60º ribs, and the 60° V-shaped ribs and the (+) 60° ribs had almost the same levels of the thermal performance since the 60° V-shaped ribs produced the highest heat (mass) transfer enhancement but also produced highest pressure drops. For the larger inlet cases, the (+) 60° ribs produced the highest values, then came the case of the 60° V-shaped ribs, and the thermal performance for the (–) 60º ribs was the lowest. The Reynolds stress model (RSM) showed well flow fields and heat transfer distributions but underpredicted average Nusselt number ratios.

level, the standard error of the intercept is underestimated whereas the standard error of the regression coefficients associated with the covariate of the intermediate level and the remaining crossed factor are overestimated. When the ignored crossed factor is at the intermediate level, only the standard error of the regression coefficients associated with the covariate of the bottom level is overestimated. In Study Two, longitudinal multilevel data were generated mirroring studies in which students are measured repeatedly and change schools over time. It was found that when the school level is modeled hierarchically above the student level rather than as a crossed factor, part of the variance at the school level is added to the student level, causing underestimation of the school-level variance and overestimation of the studentlevel variance and covariance. The standard errors of the intercept and the regression coefficients associated with the school-level predictors are underestimated, which may cause spurious significance for results. The findings of the dissertation enhanced our understanding of the functioning of CCREMs in both cross-sectional and longitudinal multilevel data. The findings can help researchers to determine when CCREMs should be used and to interpret their results with caution when they misspecify CCREMs.

Colloidal solvents, containing dispersed nanometer (~1-100 nm) sized particles, are categorized as nanofluids. With the growing heat loads in engineering systems that exceed the current technological limits, nanofluids are considered as an attractive option for more efficient heat removal for thermal management applications. Recent results reported in the literature show that the thermo-physical properties of coolants are enhanced considerably when seeded with very minute concentrations of nanoparticles. Hence, nanofluids research has provoked interest in thermal management applications. The convective heat transfer characteristics of nanofluids are reported in this study. Exfoliated graphite nanoparticles were dispersed in poly-alpha-olefin (PAO) at concentrations of 0.3% and 0.6% (by weight). The heat flux into a convective cooling apparatus was monitored and the results for nanofluid and the base fluid are presented. Thermo-physical properties of the nanofluid were measured and compared with the base fluid. The thermo-physical properties of the fluid are observed to increase with the addition of the nanoparticles. The specific heat of nanofluid was increased by ~50% compared to PAO. The thermal diffusivity was enhanced by ~400% compared to PAO. The viscosity of the nanofluid was enhanced by 10-1000 times compared to PAO. The viscosity of the nanofluid was observed to increase with temperature while the viscosity of PAO decreases with temperature. The convective heat flux was enhanced by the nanofluids by up to ~8 % for experiments performed at different heat inputs. The experimental results show that the convective heat transfer enhancement potentially results from the precipitation of nanoparticles on the heated surface and results in enhanced heat transfer surfaces (“nano-fins”).

Magnetic dependence of low temperature specific heat down to 0.6K is used to investigate the pairing symmetry of unconventional superconductor CeRu2. At low temperature Debye model highly deviated the 8T data serving as normal state below small magnetic anomaly shown around 6K. Based on the entropy conservation of superconducting transition, superconducting order parameters of s-wave and d-wave could not both be well described specific heat data at zero field. However, two-gap model, £GS=0.80 meV and £GL=1.01 meV, is better to describe the pairing symmetry of CeRu2. This might be the controversies among the earlier reports. Magnetic susceptibility and resistance under magnetic filed are both used to investigate the small anomaly, excluding double superconducting phase. Moreover, two rounds of specific-heat measurement both show the magnetic anomaly and might lead to an intrinsic property.