LKAB behöver kyla till sina processer för att kunna förädla järnmalm. Ökad tillgång på elektronik och efterfrågan på komfortkyla breder ut sig i samhället idag, vilket leder till ett ökat kylbehov. Flertalet gamla kylanläggningar på LKAB i Kiruna börjar uppnå sin livslängd och behöver ersättas med nya maskiner och ny teknik. Då är utbyggnad av fjärrkylanätet som idag levererar kyla till KK4, KA3 och SAK-labb/kontor extra intressant. Istället för att ersätta gamla kylmaskiner i andra byggnader med nya kan man ansluta sig till de berörda fjärrkyalnätet. Det är ett nät där absorptionskylmaskiner och frikyla tillgodoser kylbehoven vilket även är ett bra val ur en miljömässig synpunkt då man nyttjar spillvärme. Idag klarar detta system av att leverera kyla till nuvarande kunder men frågan är hur mycket mer man kan ansluta till samma nät och vart begränsningarna ligger. Tittar man bara på kylmaskinerna ska man kunna ta ut 3MW kyla vilket är tre gånger så mycket som levereras idag. Begränsningarna ligger således inte där utan det är i de olika kretsarna till/från kylmaskinerna. I denna studie har mätvärden bakåt i tiden varit nödvändiga då endast frikyla använts under tidsperioden då detta examensarbete har utförts. Problem med loggning av data, felinställda givare och avsaknad av mätare har gjort att konkreta beräkningar uteblivit. Denna studie får ses som ett första steg mot en eventuell utökning av kylnätet. Konkreta förslag på hur man ska komma vidare för att kunna utnyttja nuvarande kylanläggnings hela potential tas upp i rapporten. Kan man i framtiden bygga ut fjärrkylnätet skulle man minska elanvändningen och underhållskostnaderna då man får ett färre antal kylmaskiner. / To refine iron ore products cooling is needed at LKAB. The increase of electronic devices and comfort cooling leads to higher cooling demands everywhere in society. Many old cooling machines soon are going to reach the end of their life span and needs to be replaced at LKAB in Kiruna. The development of the current district cooling grid is therefore interesting. Instead of replacing old machines in other buildings with new ones they can be connected to the existing grid. It is consisting of two absorption machines and free cooling and delivering cooling to the buildings KK4, KA3 and SAK-lab/office. The energy to the machines came from waste heat which is good for the efficiency and for the environment. Today the cooling system can manage the demands but how much can be connected to the grid in the future and where the limitations is for the current cooling system has yet no answer. The capacity of the absorption cooling is about 3MW and it is three times more than what is delivered today. So, the limitations are not the installed capacity but instead the different circuits in and out to the cooling machines. In this study previous measurements were important because only free cooling was used during this project. Problems with sensors, logging data and missing flowmeter made it impossible to do concrete calculations. Instead this study is a first step in the right direction to development of the district cooling system well as suggestions for future work. If the grid can be used to full potential the power consumption and the maintenance cost will decrease which is good for the environment and the economy.

High Temperature Cooling, HTC, is a thermal conditioning strategy, which aims to reducemixing and transfer heat losses. Cooling capacity strongly depends on heat transfer coefficientsand offers a great response and several advantages in terms of efficiency and sustainability.Among the advantages, there is evidence that HTC offers an increment of energy efficiency ofHVAC systems, provision of healthier and more comfortable indoor climate and provide widepotentials for the applications of renewable. This principle leads to a higher energy efficiency ofwater-based radiant cooling systems.This paper intends to focus on the research of the thermal capacity and performance of a newalternative. This is where Cooling Radiant Ceiling Panels, CRCP, becomes a major innovationwithin the sector and begin to take on certain relevance. The cooling capacity curve of thisparticular CRCP panels has been only measured in an idealized room environment according toDIN EN 14240. Thus, further studies of this key parameter through climate chamber testingand Computational Fluid Dynamics simulations, CFD, are necessary. CFD particularly focuseson fluids in motion, their behavior and their influences in complex processes such as heat transfer.The fluid motion can be described through fundamental mathematical equations and it isbecoming widely used within the building sector.Two different cases are going to be investigated. The first case will determine the mostoptimal peripheral gap to enhance cooling performance through Natural Convection, NC. Thisstudy states the existence of a peripheral gap around the panels has proven to be inefficientin terms of enhancing natural convection in the climate chamber. The second case is aboutcalculating the cooling capacity as a function of the internal heat loads. The cooling capacity ofthe CRCP panels followed an expected behavior. The R-squared factor of the linear regressionwas found to be 0.986, hence, it does not affect the performance of the CRCP panels dependingon the inclusion of the IHLs.This thesis provides the necessary information for the implementation of CRCP panels anddifferent possible operating environments, including considerations, limitations and recommendationsfor future implementation of this strategy.

Conjugate heat transfer analysis has been carried out on an 89kN thrust chamber in order to evaluate whether combined discrete film cooling and regenerative cooling in a rocket nozzle is feasible. Several cooling configurations were tested against a baseline design of regenerative cooling only. New designs include combined cooling channels with one row of discrete film cooling holes near the throat of the nozzle, and turbulated cooling channels combined with a row of discrete film cooling holes. Blowing ratio and channel mass flow rate were both varied for each design. The effectiveness of each configuration was measured via the maximum hot gas-side nozzle wall temperature, which can be correlated to number of cycles to failure. A target maximum temperature of 613K was chosen. Combined film and regenerative cooling, when compared to the baseline regenerative cooling, reduced the hot gas side wall temperature from 667K to 638K. After adding turbulators to the cooling channels, combined film and regenerative cooling reduced the temperature to 592K. Analysis shows that combined regenerative and film cooling is feasible with significant consequences, however further improvements are possible with the use of turbulators in the regenerative cooling channels.

Call number: LD2668 .T4 1965 D22 / Master of Science

Cooling systems used to reduce heat stress in dairy operations require high energy, water usage, or both. Steady increases in electricity costs and reduction of water availability and an increase in water usage regulations require evaluation of passive cooling systems to cool cows and reduce use of water and electricity. A series of experiments were conducted to evaluate the use of heat exchangers buried as components in a conductive system for cooling cows. In the first experiment six cows were housed in environmentally controlled rooms with tiestall beds, which were equipped with a heat exchanger and filled with 25 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per each kind of bedding material) constituted a control group (water off), and the other 4 (2 sand and 2 dried manure) used water at 7°C passing through the heat exchangers (water on). The experiment was divided in 2 periods of 40 d, and each period involved 3 repetitions of 3 different climates (hot and dry, thermo neutral, and hot and humid). Each cow was randomly assigned to a different treatment after each repetition was over. Sand bedding remained cooler than dried manure bedding in all environments and at all levels of cooling (water on or off). Results from this experiment demonstrated that bed temperatures were lower and heat flux higher during the bed treatment with sand and water on. We also detected a reduction in core body temperatures, respiration rates, rectal temperatures, and skin temperatures of those cows during the sand and water on treatment. Feed intake and milk yield numerically increased during the bed treatment with sand and water on for all climates. No major changes were observed in the lying time of cows or the composition of the milk produced. The efficiency of conductive cooling as a heat abatement technique in dairy production is highly correlated with the distance between the cooling system and the skin of the cow and the type of bedding material used. A second experiment was conducted to identify possible improvements in the utilization of conductive cooling for cooling cows. Heat exchangers buried 12.7 cm below the surface as components in a conductive system ware evaluated in this study. Six cows were housed in environmentally controlled rooms with tie-stall beds, which were equipped with a heat exchanger and filled with 12.7 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per bedding material type) constituted a control group (water OFF), and the other four (two sand and two dried manure) used water at 7°C passing through the heat exchangers (water ON). The experiment was divided into two periods of 40 days and each period involved three repetitions of three different climates hot dry (HD), thermo neutral(TN) and hot humid (HH). Each cow was randomly assigned to a different treatment after each repetition was over. The sand and water on treatment was the most efficient treatment under heat stress conditions (humid or dry heat). Cows in stalls with the sand and water on treatment demonstrated lower rectal temperatures, respiration rates, skin surface temperatures and core body temperatures compared to the other three treatments. Additionally, the sand and water on treatment increased milk yield and resting time of cows under heat stress. Also, the sand and water on treatment had the lowest bed surface temperatures and highest heat exchange compared to the other treatments. From these two experiments we confirm that heat exchangers are a viable heat abatement technique that could reduce the heat load of heat stressed cows; however, this system should be paired with additional cooling systems (e.g. fans and or misters) to most efficiently reduce the negative effects of heat stress on dairy production. Additionally, Sand was superior to dried manure as a bedding material in combination with heat exchangers. To make further recommendations of the use of heat exchangers in commercial dairy farm, a third study was developed. Based on the data obtained in the previous experiments, a comprehensive energy balance was developed to fully understand conductive cooling in two different environments (HD and HH), two bedding materials (sand and dried manure) and two depths between cows and the heat exchangers (25 vs. 12.5 cm). The energy balance estimates indicated that sand is the most efficient bedding material when utilized as bedding material with conductive cooling in both hot dry and hot humid environments. In the hot-dry environment there was an increase in the conductive heat exchanged with the reduction in bedding depth to 12.5 cm, however this did not result in a reduction in the heat storage of cows. In the hot-humid environment when heat exchangers were placed 12.5 cm from the top of the bed there was an increase in both the conductive heat loss and heat storage of cows when compared to 25 cm. Additionally, results demonstrated that the efficiency of heat exchangers as measured by heat flux was improved when heat exchangers were at a depth of 12.5 cm. The sensibility analysis indicated that a reduction in the depth and/or an increase in the thermal conductivity of both bedding materials would maximize conductive heat exchange. These results should be utilized as recommendations for the utilization of heat exchangers and conductive cooling in commercial dairy farms. Evaporative cooling is widely used in dairy farms located in arid environments. Even though, these cooling systems have been shown to effectively reduce the heat stress of lactating dairy cows, a growing shortage of water and rising cost of electricity compromise its future usage. An experiment was developed to compare two evaporative cooling systems, their interaction with lactating dairy cows and their usage of natural resources. The efficacy of 2 evaporative cooling systems (Korral Kool, KK, Korral Kool Inc., Mesa, AZ; FlipFan dairy system, FF, Schaefer Ventilation Equipment LLC, Sauk Rapids, MN) was estimated utilizing 400 multiparous Holstein dairy cows randomly assigned to 1 of 4 cooled California-style shade pens (2 shade pens per cooling system). Each shaded pen contained 100 cows (days in milk = 58 ± 39, milk production = 56 ± 18 kg/d, and lactation = 3 ± 1). Production data (milk yield and reproductive performance) were collected during 3 months (June–August, 2013) and physiological responses (core body temperature, respiration rates, surface temperatures, and resting time) were measured in June and July to estimate responses of cows to the 2 different cooling systems. Water and electricity consumption were recorded for each system. Cows in the KK system displayed slightly lower respiration rates in the month of June and lower surface temperatures in June and July. However, no differences were observed in the core body temperature of cows, resting time, feed intake, milk yield, services/cow, and conception rate between systems. The FF system used less water and electricity during this study. In conclusion, both cooling systems (KK and FF) were effective in mitigating the negative effects of heat stress on cows housed in arid environments, whereas the FF system consumed less water and electricity and did not require use of curtains on the shade structure. Results of this research indicate that effective use of conductive cooling in combination with efficient evaporative cooling systems offer opportunities to reduce both water and electricity consumption on dairy farms under both hot dry and hot humid environments.

Advances in the field of semiconductor physics have allowed for rapid development of new, more powerful devices. The new fabrication techniques allow for reductions in device geometry, increasing the possible wafer packing density. The increased output power comes with the price of excessive heat generation, the removal of which proves problematic at such scales for conventional cooling systems. Consequently, there is a rising demand for new cooling systems, preferably those that do not add large amount of additional bulk to the system. One promising system is the thermoelectric (TE) cooler which is small enough to be integrated onto the device wafer. Unlike more traditional gas and liquid coolers, TE coolers do not require moving parts or external liquid reservoirs, relying only on the flow of electrons to transport heat energy away from the device. Although TE cooling provides a neat solution for the extraction of heat from micron scale devices, it can normally only produce small amounts of cooling of 1-2 Kelvin, limiting its application to low power devices. This research aimed to find ways to enhance the performance of the TE cooler using detailed simulation analysis. For this, a self consistent, semi-classical, ensemble Monte Carlo model was designed to investigate the operation of the TE cooler at a higher level than would be possible with experimental measurements alone. As part of its development, the model was validated on a variety of devices including a Gunn diode and two micro-cooler designs from the literature, one which had been previously simulated and another which had been experimentally analysed. When applied to the TE cooler of focus, novel operational data was obtained and signification improvements in cooling power were found with only minor alterations to the device structure and without need for an increase in volume.

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