No description available.

No description available.

This experimental study explores the heat transfer from heated bare and finned tubular surfaces to particulates in packed bed cross flow. The results from this experiment will be used to help select the type of particulates that will be used. Additionally, these results will assist in estimating heat transfer in prototype and commercial particle to fluid heat exchangers (PFHX). This research is part of larger effort in the use of particulates in concentrating solar power technology. These solid particles are heated by concentrated sunlight to very high temperatures at which they are a suitable heat source for various thermal power and thermochemical cycles. Furthermore, one of the advantages of this concept is the ability to store thermal energy in the solid particles at relatively low cost. However, an important feature of any Particle Heat Receiver (PHR) system is the PFHX, which is the interface between the solar energy system and the thermal power or chemical system. In order to create this system material data is needed for the design and optimization of this PFHX. The paper focuses on the heat transfer properties of particulates to solid surfaces under plug flow conditions. The particulates will be evaluated for three grain sizes of sand and two grain sizes of proppants. These two materials will be tested at one, five and ten millimeters per second in order to see how the various flow rates, which will be required for different loads, will affect the heat transfer coefficient. Finally the heat transfer coefficient will also be evaluated for both finned and non-finned heat exchangers to see the effect that changes in the surface geometry and surface area have on the heat transfer coefficient. The heat transfer coefficient will help determine the appropriate material that will be used in the PHR system.

Concern with global climate change has led to the interest in the use of natural refrigerants, such as carbon dioxide, as replacements in heat pump systems. When operating in a transcritical cycle, carbon dioxide heat pumps are well suited for use in high temperature water heating heat pumps. In this work, four systems are analyzed: with and without the use of a suction line heat exchanger, and two water heating schemes. These two schemes involve the heating of water to its desired temperature at a low water flow rate in a single pass through the heat pump, and the heating of water at a high water flow rate, but requiring multiple passes. The performance and resulting heat exchanger size of these four systems is analyzed through the development of an overall system model. This system model uses component-level models that were developed based upon heat exchanger geometry and subsequently validated through experimental testing on a test facility developed for this purpose.

The large proportion of energy used in the built environment has made improving energy efficiency in buildings, in particular their heating, ventilation, and air conditioning (HVAC) systems, a policy objective for reducing energy consumption and CO2 emissions nationally and internationally. Ground source heat pump (GSHP) systems, due to their high coefficient of performance (COP) and low CO2 emissions are consequently, receiving increasing attention. This work is concerned with the modelling of borehole heat exchangers (BHEs), the commonest form of ground heat exchangers found in GSHP systems. Their careful design is critical to both the short timescale and long timescale performance of geothermal heat pump systems. Unlike conventional components of HVAC systems, BHEs cannot be designed on the basis of peak load data but require 3 application of dynamic thermal models that are able to take account of the heat transfer inside the borehole as well as the surrounding ground. The finite volume method has been applied to develop a dynamic three-dimensional (3D) model for a single BHE and BHE arrays. The multi-block boundary fitted structured mesh used in this model allows the complex geometries around the pipes in BHEs and the surrounding ground around the borehole to be represented exactly. The transport of the fluid circulating along the pipe loop has been simulated explicitly in this model. The ground underneath the borehole has also been represented in this model. Validation of the 3D model has been carried out by reference to analytical models of borehole thermal resistance and fluid transport in pipes, as well as experimental data. In this work, the 3D numerical model has been applied to investigate the three-dimensional characteristics of heat transfer in and around a BHE at both short and long timescales. By implementing a two-dimensional (2D) model using the same numerical method and comparing the simulation results from the 3D and 2D models, the most significant three-dimensional effects have been identified and quantified. The findings have highlighted some of the limitations of 2D models, and based on the findings, methods to improve the accuracy of a 2D model have been suggested and validated. Furthermore, the 3D and 2D finite volume models have been applied to simulate an integrated GSHP system and their effects on overall system performance predictions have been investigated. The 3D numerical model has also been applied to examine thermal interactions within BHE arrays and to evaluate the assumptions of the line source model and their implications in the analysis of thermal response test data.

The main objective of this thesis is to investigate the transient response and steady-state performance of a counter-cross flow liquid-to-air membrane energy exchanger (LAMEE). The LAMEE is constructed from several semi-permeable membranes which separate the air and liquid streams. In addition to heat transfer, moisture transfer occurs between the air and liquid streams since the membranes are permeable to water vapor. The LAMEE performance is assessed experimentally and the results are used to verify a numerical model. The verified numerical model is also used to extrapolate the transient and steady-state performance parameters to other test conditions. The transient response of the LAMEE is important since there are times when the LAMEE operates under transient conditions due to daily start-up or changing operating conditions such as flow rates, temperatures or humidities. The transient response of the LAMEE is investigated experimentally and numerically. The number of heat transfer units (NTU), and the ratio of solution and air heat capacity rates (Cr*) are two important parameters that affect the LAMEE performance. The results show that the transient sensible, latent and total effectivenesses increases with time after a step change in the conditions of the inlet liquid desiccant. The experimental and numerical transient effectiveness values and trends are compared for different NTU and Cr* values under summer and winter test conditions and the results show satisfactory agreement. In addition to the transient effectiveness, the time constant of the LAMEE is assessed as an important transient parameter. The time constant represents the time it takes for the LAMEE to reach 63.2% of the steady-state conditions after a step change in inlet conditions. The transient response of the outdoor air temperature and humidity ratio are normalized and used to determine the sensible and latent time constants. It is found that time constant depends on NTU, Cr* and thermal mass capacity of the LAMEE. The experimental and numerical results show that time constant increases as Cr* decreases or NTU increases. Furthermore, the verified numerical model is used to study the effect of outdoor air conditions on the LAMEE time constant. The numerical results reveal that the latent time constant is influenced by outdoor air conditions and the time constant decreases as H* increases, but the sensible time constant is almost constant for various outdoor air conditions. However, the outdoor air conditions affect the transient response of the LAMEE considerably since the total transient response of the LAMEE is closer to the latent transient response for the conditions studied. The steady-state performance of the LAMEE is studied for different NTU and Cr* values under summer test conditions. The experimental data are compared to numerical and analytical results and acceptable agreement is achieved. It is found that the steady-state effectiveness of the LAMEE increases with NTU and Cr*. The maximum total effectiveness reaches 88% for NTU=10 and Cr*=6.3. The verified numerical model is also used to investigate the effect of outdoor air conditions on the steady-state sensible and latent effectiveness of the LAMEE. The sensible effectiveness is significantly influenced by outdoor air conditions variation while the latent effectiveness is only slightly influenced by these variations. The sensible effectiveness decreases as the operating condition factor (H*) increases, but the latent effectiveness increases with H*.

Volatile Organic Compounds (VOCs) constitute an important class of indoor air contaminants and they may cause adverse health effects for occupants in buildings. Indoor generated contaminants may be transferred between the supply and exhaust air streams of the building’s Heating, Ventilation and Air-conditioning (HVAC) system when air-to-air energy recovery devices are used. The run-around membrane energy exchanger (RAMEE) is a novel exchanger, which uses aqueous magnesium chloride (MgCl2) salt solution (34-35 wt%) as a liquid desiccant to transfer heat and moisture between remote supply and exhaust air streams. In the RAMEE, a gas-phase porous membrane is placed between the air stream and the liquid desiccant stream in each exchanger and the membrane prevents the salt solution from entering the air stream but still allows the transfer of water vapor through the semi-permeable membrane. In the RAMEE, VOCs may transfer between the exhaust and supply air streams due to (i) air leakage or (ii) due to dissolution of VOCs into the liquid desiccant in the exhaust exchanger and their subsequent evaporation into the air stream of the supply exchanger. These two transfer mechanisms were tested in the laboratory using two counter-cross-flow RAMEE prototypes (Prototype #4 and Prototype #6). Tests were conducted at different air and desiccant flow rates at AHRI standard summer and winter operating conditions. Sulfur hexafluoride (SF6) was used as a tracer gas to test air leakage and toluene (C7H8) and formaldehyde (HCHO) were used to test VOC dissolution and transfer. From an external source, a known concentration of VOC was injected into the exhaust air inlet stream and the transfer fraction of VOC to the supply air stream was calculated. This transfer fraction or Exhaust Air Transfer Ratio (EATR) defined by ANSI/ASHRAE Standard 84 (2012) at steady state conditions was used to quantify and compare the transfer fraction of contaminants in both prototypes. The uncertainty in the transfer fraction was calculated and all the uncertainty bounds were calculated for 95% confidence interval. The transfer fraction of sulfur hexafluoride was 0.02 +/- 3.6% for both prototypes tested, which means that the air leakage between the air streams is negligible. The transfer of toluene, which has a low solubility in water, was less than the uncertainty in the measurement. EATR* values for toluene were 2.3-3.4% and the uncertainties were 3.4-3.6%. The transfer of formaldehyde between the exhaust and the supply air streams was the highest and the EATR* values just exceeded the uncertainties in the EATR* measurement. The highest EATR* values for the transfer of formaldehyde in Prototype #4 and Prototype #6 were 6.4 +/- 3.6% and 5.3 +/- 3.6%, respectively. At steady state, the measured EATR* values for both prototypes were insensitive to changes in the air flow rate, the liquid desiccant flow rate, the latent effectiveness and the environmental conditions but time delays to reach steady state were significant. These results imply that there is a negligible transfer of contaminants due to air leakage between the air streams, a negligible transfer of low water soluble VOCs (such as toluene), but possibly a small detectable transfer of very water soluble VOCs (such as formaldehyde) between the exhaust and supply air streams of the RAMEE.

Detta examensarbete utfördes på uppdrag av Umeå Kommun. Uppgiften bestod av att utvärdera dagens användning av en borrhålsbrunn samt undersöka vad som är det optimala användningsområdet för borrhålsbrunnen. Borrhålsbrunnen används i dagsläget för att förvärma samt kyla utomhusluft in till kontorsbyggnaden Kubens ventilationsaggregat. Ventilationens förvärmning består av två delar, en markkanal och ett geoenergibatteri. Viktiga parametrar hos förvärmningen analyserades med hjälp av mätvärden för temperatur och flöde. Resultaten jämfördes därefter med alternativet att använda borrhålsbrunnen tillsammans med en värmepump. Då borrhålsbrunnens kapacitet inte var tillräcklig för att klara byggnadens hela uppvärmningsbehov, undersöktes det hur en värmepump skulle kunna köras i kombination med fjärrvärme. Två driftstrategier, Bas och Kapatoppar, undersöktes. Bas leverar en basproduktion under hela vinterperioden medan Kapatoppar startar vid -6°C för att sänka effekttoppar. Utvärderingen av förvärmningen visade att geoenergibatteriet är mer kompatibelt med ventilationsaggregat av VAV-typ (Variable Air Volume) än vad markkanalen är. Däremot är inte förvärmning i kombination med roterande värmeväxlare ett bra koncept för byggnaden som den används idag. På grund av att förvärmningen är placerad före den roterande värmeväxlaren så är bara 15-20 % av förvärmningseffekterna energibesparande. Detta kombinerat med en optimerad drift av aggregatet sett till tidsstyrning och behovsstyrning av flöde gör att förvärmningen har en liten påverkan både på byggnadens maximala effektbehov och totala energibehov. Att köra värmepump i kombination med fjärrvärme för uppvärmning var ekonomiskt lönsamt främst på grund av att värmepumpen kunde kapa byggnadens effektoppar. Kostnaden för storleken på den abonnerade effekten uppgår idag till drygt 40 % av den totala fjärrvärmekostnaden. Dagens relation mellan el- och fjärrvärmepriser bidrog naturligtvis också till att värmepumpsalternativet var lönsamt. För de undersökta förutsättningarna så blev paybacktiden för en värmepump med den lönsammaste driftstrategin, Bas, 4,4 år.

Boron is an element, which is necessary as essential nutrient for living organisms, especially for plants where it is involved in cell wall composition. But boron excess can cause some problems on the development of plants (defoliation, decay and fall unripe fruits), of humans and animals such as nausea, diarrhoea, dermatitis, lethargy. Boron toxicity also changes blood composition, caused disorder in neurological, physical, intellectual development. Nowadays, due to the shortage of fresh water sources, seawater desalination has been becoming an alternative fresh water supply. However, the presence of boron in seawater is quite high (4.5 mg L–1, around 4.5 mM). Moreover, the increasing use of boron in industries and its discharge to the environment has led to the contamination of surface and ground waters. As the result, boron removal, in production of drinking water becomes very important. Therefore, the World health organization has recommended a guideline of 0.5 mg L–1 B in drinking water and a maximum limit of 0.3 mg L–1 B in fresh water used for irrigation. The objective of this thesis is to study the mechanisms of boron surface exchange on different materials versus time and at equilibrium depending on some physicochemical parameters such as pH, initial boron concentration, reaction time in order to find a new exchanger for boron removal. Boron removal was carried out by ion exchange process using 2 types of resins: Amberlite IRA 743, Diaion CRB 03 as boron selective resins with methylglucamine functions, and Ambersep 900-OH and Amberlite IRA 402 Cl as anionic exchange resins with ammonium functions. From batch studies, fast exchange between resin surface and liquid phase was observed with boron removal up to at least 96 % within 30 min for Amberlite IRA 743, Diaion CRB 03 and Ambersep 900- OH. The reaction between resin surface and boron solution reached equilibrium after 2 h for all the resins. The pseudo-second order kinetic model was used to well describe the sorption kinetic process of the resins. At equilibrium, the experimental results showed that the maximum adsorption was observed to be achieved at pH 8 for Ambersep 900- OH, pH 10 for Amberlite IRA 402 Cl and independent on pH range from 6 to 12 for the 2 boron selective resins Amberlite IRA 743 and Diaion CRB 03. At pH 8 and for boron concentrations < 20 mM, the Langmuir-type relationship was used to fit the experimental data for Amberlite IRA 743, Ambersep 900- OH and resin Diaion CRB 03. In the range of studied boron concentration, the boron sorption onto Amberlite IRA 402 Cl followed linear-type behaviour. At pH 8 and for boron concentrations < 20 mM, the sorption capacities are: 1, 0,7, 0,3 et 0,05 mmol g–1 for Diaion CRB 03, Amberlite IRA 743, Ambersep 900- OH and Amberlite IRA 402 Cl, respectively. Column experiments were performed with the anionic resin Ambersep 900-OH and the selective one Amberlite IRA 743 by studying both the influence of boron concentration and the residence time. For the selective resin, if the residence time decreases, the boron breakthrough is fast followed by a long tail. For larger residence time, local equilibrium seems to be assumed. Results are thus consistent with batch experimental data. For the anionic resin, the nonlinear behaviour is also confirmed. Moreover, column experiments showed a strong difference during desorption. To regenerate resins, acid and basic treatments are necessary for the selective resin although a basic solution is enough for the anionic resin. A more detailed study of mechanisms is in progress in order to build a exchange model for predicting boron fate. Finally, characterization of pectins was also performed. Its composition (sugar and boron content) and the viscosity of pectin solutions were quantified. Filtration experiments allowed testing the efficiency of such material to remove boron too

Inorganic cations play decisive roles in many cellular and physiological processes and are essential components of plant nutrition. Therefore, the uptake of cations and their redistribution must be precisely controlled. Vacuolar antiporters are important elements in mediating the intracellular sequestration of these cations. CAXs (for CAtion eXchanger) are members of a multigene family and appear to predominately reside on vacuoles. Defining CAX regulation and substrate specificity have been aided by utilizing yeast as an experimental tool. Studies in plants suggest CAXs regulate apoplastic Ca2+ levels in order to optimize cell wall expansion, photosynthesis, transpiration and plant productivity. CAX studies provide the basis for making designer transporters that have been used to develop nutrient enhanced crops and plants for remediating toxic soils. In my second study, I have characterized and defined autoinhibitory domain of Arabidopsis CAX3. Several CAX transporters, including CAX1, appear to contain an approximately 40 amino acid N-terminal regulatory regions (NRR) that modulates transport through N-terminal autoinhibition. Deletion of the NRR from several CAXs (sCAX) enhances function in plant and yeast expression assays; however, to date, there are no functional assays for CAX3. In this report, we create a series of truncations in the CAX3 NRR and demonstrate activation of CAX3 in both yeast and plants by truncating a large portion of the NRR. Experiments on endomembrane-enriched vesicles isolated from yeast expressing activated CAX3 demonstrate that the gene encodes Ca2+/H+ exchange with properties distinct from CAX1. These studies demonstrate shared and unique aspects of CAX1 and CAX3 transport and regulation. My third study is to express and purify CAX proteins for X-ray crystallographic analysis. In this study, I initiated crystallization of vacuolar membrane localized CAX protein from eukaryotes. Membrane proteins continue to be challenging targets for structural biology because of their hydrophobic nature. We have demonstrated here that eukaryotic Ca2+/H+ exchanger can be successfully expressed in E. coli based expression system. Collectively, our findings suggest that CAX protein can be successfully expressed, detergent solublized and purified from E. coli with a yield sufficient for functional and structural studies.