The Cu-Cl thermochemical cycle is a promising method to generate hydrogen as a clean fuel for human use in the future. The cycle can be coupled to nuclear reactors to supply its heat requirements. The cycle generates hydrogen by splitting water molecules through a series of chemical reactions. Thermal management within the cycle is crucial for improving its thermal efficiency. The cycle has an average theoretical efficiency of around 46% without any heat recovery. The efficiency may increase up to 74%, if all heat associated with the products of the cycle’s steps is recycled internally. The products of the different processes that transfer heat are; oxygen, hydrogen, and molten CuCl. The heat carried by oxygen and hydrogen can be recovered by the use of conventional heat exchangers. However, recovering heat from molten CuCl is very challenging due to the phase transformations that molten CuCl undergoes, as it cools down from liquid to solid states. This thesis presents a new model that predicts the fluid flow and heat transfer in a direct contact heat exchanger, designed to recover the heat from molten CuCl, through the physical interaction between CuCl droplets and air. Numerical results for the variations of temperature, velocity, heat transfer rate, and so forth, are given for two cases of CuCl flow. The predicted dimensions of the heat exchanger were found to be a diameter of 0.13 m, and a height of 0.6 and 0.8 m for 1 and 0.5 mm droplet diameters, respectively. The results obtained provide valuable insights for the equipment design and scale-up of the Cu-Cl cycle. / UOIT

Modelling the energy exchange between the snowpack and the atmosphere is critical for many hydrological applications. Of the terms present in the snow energy balance, the turbulent fluxes of sensible and latent heat are the most challenging to estimate, particularly within mountain environments where the hydrological importance is great. Many of the flux estimation techniques, such as the bulk transfer method, are poorly adapted for use in complex terrain. In order to characterize the turbulence and to assess the suitability of flux estimation techniques, eddy covariance flux measurements and supporting meteorological data were collected from two mountain valley forest openings in Kananaskis Country, AB. These sites were generally calm, however wind gusts were frequently observed which markedly affected the turbulence characteristics and increased the rates of momentum and heat transfer. In order to successfully apply the bulk transfer technique at these sites, it was necessary to use environment-specific transfer coefficients to account for the effect of the surrounding complex terrain. These observations were compared with data collected on a treeless alpine ridge near Whitehorse, YT, where it was found that many of the turbulence characteristics were similar to flat sites. However, the boundary layer formed over the alpine ridge was very thin and the site was poorly suited for estimating surface fluxes. The mountain results were further contrasted with data collected over a homogeneous and flat prairie site located near Saskatoon, SK. This site included measurement of all of the snow energy terms, permitting an estimate of the energy balance closure obtainable over snow surfaces. The observed energy balance residual was very large, indicating that the eddy covariance technique was unable to capture all of the turbulent energy. It was concluded that an unmeasured transfer of sensible heat was occurring which was strongly correlated with the long-wave radiation balance. Mechanisms for this relationship were hypothesized. Two snow energy balance models were used to investigate the energy imbalance, where it was observed that the flux terms could be suitably simulated if effective parameters were used to augment the sensible heat transfer rate. The results from this thesis contribute to the understanding of heat transfer processes over snow surfaces during mid-winter conditions and improve the ability to model turbulent heat and mass fluxes from snow surfaces in complex environments.

Experiments were performed to study forced convective heat transfer of de-ionized water (DI water) and aqueous nanofluids flowing in a microchannel. An array of temperature nanosensors, called “Thin Film Thermocouples (TFT)”, was utilized for performing the experimental measurements. TFT arrays were designed (which included design of photomask layout), microfabricated, packaged and assembled for testing with the experimental apparatus. Heat removal rates from the heated surface to the different testing fluids were measured by varying the coolant flow rates, wall temperatures, nanoparticle material, nanoparticle morphology (shape and nanoparticle size) as well as mass concentrations of nanoparticles in the coolants. Anomalous thermal behavior was observed in the forced convective heat transfer experiments. Precipitation of the nanoparticles on the heat exchanging surface was monitored using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray spectroscopy (EDX). Isolated precipitation of nanoparticles is expected to cause formation of “nanofins” leading to enhancement of surface area and thus resulting in enhanced convective heat transfer to the nanofluid coolants. However, excessive precipitation (caused due to the agglomeration of the nanoparticles in the nanofluid coolant) causes scaling (fouling) of the heat exchanging surfaces and thus results in degradation of convective heat transfer. This study shows that the surface morphology plays a crucial role in determining the efficacy of convective heat transfer involving suspensions of nanoparticles in coolants (or nanofluids). Flow visualization and quantitative estimation of near-wall temperature profiles were performed using quantum dots and fluorescent dyes. This non-contact measurement technique for temperature and flow profiles in microchannels using quantum dots is expected to make pioneering contribution to the field of experimental flow visualization and to the study of micro/nano-scale heat transfer phenomena, particularly for forced convective heat transfer of various coolants, including nanofluids. Logical extensions of this study were explored and future directions were proposed. Preliminary experiments to demonstrate feasibility showed significant enhancement in the flow boiling heat flux values for nanofluids compared to that of pure solvent (DIW). Based on the novel phenomena observed in this study several other topics for future research were suggested, such as, using Surface Plasmon Resonance (SPR) platforms to monitor precipitation of nanoparticles on microchannel surfaces in real time (e.g., for generating surface isotherms).

Due to rising energy prices as well as supply and ecological concerns, there is a strong interest in reducing the energy used in buildings. As such, it is desirable to model the operation of a building and predict its future energy use. In predicting the energy use of a building, the heat gain/loss through windows is an important factor. In order to accurately model this heat gain/loss, the convective heat transfer coefficient of any insect screens mounted adjacent to the windows needs to be known. This thesis describes an investigation into the heat transfer from insect screens mounted towards the indoor side of a window. The convective heat transfer coefficient of an insect screen varies based on several parameters. For implementation in building energy modelling software, it is desirable to be able to predict the convective heat transfer coefficient for an arbitrary insect screen. Due to the number of variables and the large dynamic range of the details required for modelling, direct simulation of a range of whole insect screens was not completed. Instead, a range of numerical models representing small sections of an insect screen were created. By comparing results from these to available correlations for simpler geometries, such as cylinders and flat plates, estimates for the heat transfer coefficient of a screen can be obtained. The results were non-dimensionalized for analysis and different methodologies for the prediction of heat transfer from an indoor window insect screen are described.

Modelling the energy exchange between the snowpack and the atmosphere is critical for many hydrological applications. Of the terms present in the snow energy balance, the turbulent fluxes of sensible and latent heat are the most challenging to estimate, particularly within mountain environments where the hydrological importance is great. Many of the flux estimation techniques, such as the bulk transfer method, are poorly adapted for use in complex terrain. In order to characterize the turbulence and to assess the suitability of flux estimation techniques, eddy covariance flux measurements and supporting meteorological data were collected from two mountain valley forest openings in Kananaskis Country, AB. These sites were generally calm, however wind gusts were frequently observed which markedly affected the turbulence characteristics and increased the rates of momentum and heat transfer. In order to successfully apply the bulk transfer technique at these sites, it was necessary to use environment-specific transfer coefficients to account for the effect of the surrounding complex terrain. These observations were compared with data collected on a treeless alpine ridge near Whitehorse, YT, where it was found that many of the turbulence characteristics were similar to flat sites. However, the boundary layer formed over the alpine ridge was very thin and the site was poorly suited for estimating surface fluxes. The mountain results were further contrasted with data collected over a homogeneous and flat prairie site located near Saskatoon, SK. This site included measurement of all of the snow energy terms, permitting an estimate of the energy balance closure obtainable over snow surfaces. The observed energy balance residual was very large, indicating that the eddy covariance technique was unable to capture all of the turbulent energy. It was concluded that an unmeasured transfer of sensible heat was occurring which was strongly correlated with the long-wave radiation balance. Mechanisms for this relationship were hypothesized. Two snow energy balance models were used to investigate the energy imbalance, where it was observed that the flux terms could be suitably simulated if effective parameters were used to augment the sensible heat transfer rate. The results from this thesis contribute to the understanding of heat transfer processes over snow surfaces during mid-winter conditions and improve the ability to model turbulent heat and mass fluxes from snow surfaces in complex environments.

The gas turbine blade/vane internal cooling is achieved by circulating the compressed air through the cooling passages inside the turbine blade. Leading edge and trailing edge of the turbine blade are two critical regions which need to be properly cooled. Leading edge region receives extremely hot mainstream flow and high heat transfer enhancement is required. Trailing edge region usually has narrow shaped geometry and applicable cooling techniques are restricted. Heat transfer will be investigated in the leading edge and trailing edge cooling channels at high rotation numbers close to the engine condition. Heat transfer and pressure drop has been investigated in an equilateral triangular channel (Dh=1.83cm) to simulate the cooling channel near the leading edge of the gas turbine blade. Three different rib configurations (45°, inverted 45°, and 90°) were tested at four different Reynolds numbers (10000-40000), each with five different rotational speeds (0-400 rpm). By varying the Reynolds numbers (10000-40000) and the rotational speeds (0-400 rpm), the rotation number and buoyancy parameter reached in this study were 0-0.58 and 0-2.3, respectively. 45° angled ribs show the highest thermal performance at stationary condition. 90° ribs have the highest thermal performance at the highest rotation number of 0.58. Heat transfer coefficients are also experimentally measured in a wedge-shaped cooling channel (Dh =2.22cm, Ac=7.62cm2) to model an internal cooling passage near the trailing edge of a gas turbine blade where the coolant discharges through the slot to the mainstream flow. Tapered ribs are put on the leading and trailing surfaces with an angle of attack of 45°. The ribs are parallel with staggered arrangement on opposite walls. The inlet Reynolds number of the coolant varies from 10,000 to 40,000 and the rotational speeds varies from 0 to 500 rpm. The inlet rotation number is from 0 - 1.0. The local rotation number and buoyancy parameter are determined by the rotational speeds and the local Reynolds number at each region. Results show that heat transfer is high near the regions where strong slot ejection exists. Both the rotation number and buoyancy parameter have been correlated to predict the rotational heat transfer enhancement.

No description available.

Spray cooling is one of the most promising technologies in applications which require large heat removal capacity in very small areas. Previous experimental studies have suggested that one of the main mechanisms of heat removal in spray cooling is forced convection with strong mixing due to droplet impingement. These mechanisms have not been completely understood mainly due to the large number of physical variables, and the inability to modulate and control variables such as droplet frequency and droplet size. Our approach consists of minimizing the number of experimental variables by controlling variables such as droplet direction, velocity and diameter. A study of heat transfer for single and multiple droplet impingements using HFE- 7100 as the cooling fluid under constant heat flux conditions is presented. Monosized single and multiple droplet trains were produced using a piezoelectric droplet generator with the ability to adjust droplet frequency, diameter, velocity, and spacing between adjacent droplets. In this study, heaters consisting of a layer of Indium Tin Oxide (ITO) as heating element, and ZnSe substrates were used. Surface temperature at the liquid-solid interface was measured using Infrared Thermography. Heat transfer behavior was characterized and critical heat flux was measured. Film thickness was measured using a non-invasive optical technique inside the crown formation produced by the impinging droplets. Hydrodynamic phenomena at the droplet impact zone was studied using high speed imaging. Impact regimes of the impinging droplets were identified, and their effect on heat transfer performance were discussed. The results and effects of droplet frequency, droplet diameter, droplet velocity, and fluid flow rate on heat flux behavior, critical heat flux, and film morphology were elucidated. The study showed that forced heat convection is the main heat transfer mechanism inside the crown formation formed by droplet impingement and impact regimes play an important role on heat transfer behavior. In addition, this study found that spacing among adjacent droplets is the most important factor for multiple droplet stream heat transfer behavior. The knowledge generated through the study provides tools and know-how necessary for the design and development of enhanced spray cooling systems.

Steel is the mother of industry, and is also an energy consumption intensive industry. Since the energy crisis, the various countries iron and steel plants positively take each energy frugal measure in order to reduce the fuel and the electric power consumption. In the iron and steel plant comparatively consumes the energy the system regulation equipment is the reheating furnace, so to save energy in a reheating furnace and reduce the energy consumption become one of important topics. The reduction consumes energy the countermeasure aspect may by analyze the heat transfer model and the change reheating furnace characteristic begins. In this thesis, we will build a simulation system of reheating furnace to analysis the temperature change of slab in a reheating furnace and discussion energy consumption factor. And then we use the thermal balance model to analysis the situation of fuel consumption. According to different conditions, we want to discuss the relationships energy consumption and increasing temperature of slab inside furnace.

Abstract Steel is the mother of industry, and is also an energy consumption intensive industry. Especially for the rolling mill, the energy consumption in a reheating furnace take a half, so to save energy in a reheating furnace and reduce the energy consumption become the major issue in the future. The reheating furnace used in general process of steel producing can divided into two types-Continuous type and Batch type- through its ability of steel rolling¡Napproach and its demand. In this thesis, our research target is the batch type reheating furnace, we based on theory of heat transfer in a reheating furnace to build a simulation system of reheating furnace and calculate the temperature-time curve of slab and its heat flux. And then we use the thermal balance model to analysis the situation of fuel consumption. According to different operated conditions, we want to discuss the relationships between energy consumption and increasing temperature of slab inside furnace¡Nsoaking degree¡C From analysis result, we can find that fixed the total time in furnace, the longer of heating time is, the lower of average temperature of slab and the higher of temperature difference of discharge slab are. But in the process of increasing temperature, the max temperature difference of slab is lower. Using the exhaust gas to preheat air through the heat exchanger, we can find that when the temperature of preheated air is increasing, the heat loss of exhaust gas and fuel consumption will be lower. When air-fuel ratio is getting higher, the temperature difference in the process of increasing temperature will be getting lower, and it will be higher as the slab soaks. When air-fuel ratio is increasing, the quantity of fuel consumption will increase too. In respect of refractory material, heat loss of furnace and accumulation of heat in refractory material caused by using the refractory cottons is less than using the refractory bricks. Besides that, the different fuel will only affect the quantity of fuel consumption, not increasing temperature of slab and soaking degree.