I takt med stigande energipriser finner fler och fler det lönsamt att installera värmepump för att reducera sitt energibehov. Värmepumpar har dock svårigheter att tillgodose värmebehovet när utomhustemperaturen sjunker under -10°C. Detta problem kan minskas med så kallade economizerkopplingar, denna rapport jämför de båda economizersystemen flash tank cycle (FTC) och internal heat exchanger cycle (IHXC). Eftersom det har visat sig att vinsterna med economizerkopplingar är som störst då temperaturlyftet är stort är det mest intressant att jämföra dem i luft/vatten värmepumpar. Detta på grund av att övriga applikationer som berg-, jord- eller luft/luft-värmepumpar inte utsätts för samma stora temperaturvariation då utetemperaturen faller. Därför avgränsades rapporten till att endast omfatta economizerkopplingar i luft/vatten värmepumpar. Syftet i rapporten har växt fram ur den strävan som finns i att ständigt energieffektivisera vår bostadssektor vad det gäller uppvärmning, där värmepumpar idag har en viktig roll. Bakgrunden i rapporten är relativt omfattande för att ge läsaren den nödvändiga informationen för att sätta sig in i resultatet. Bakgrunden, eller den allmänna tekniska beskrivningen, innehåller bland annat övergripande beskrivningar beträffande de vanliga komponenterna i en värmepump, definition på en economizer samt vilka möjligheter economizern ger. Metoden för arbetet bestod i en litteraturgranskning där jämförelser som lett fram till resultatet togs ur artiklar från andra experimentella försök inom området. Nyckeltal som jämfördes var COP (Coefficient Of Performance), elanvändning, kyleffekt och värmeeffekt vid låga förångningstemperaturer. Resultaten pekade på att FTC-systemet har en fördel jämtemot IHXC vid kallare klimat på grund av sin bättre värmeeffekt och högre COP. Däremot drogs slutsatsen att IHXC har fördelar som noggrann reglerkapacitet och större tolerans vid val av köldmedie eftersom ingen fasseparation med tillkommande problem sker i denna koppling. När värmepumpsprocessen vänds och används till kylning kommer rapporten fram till att skillnaden mellan de två systemen är försumbar.

no / An economizer, one type of heat exchangers, is specifically named to carry out heat exchange between hot gas and water. It is considered in this work to provide heat recovery between exhaust gas and boiler's feed water. As it has been studied to obtain high heat recovery with several designs, here the economizer is devised with new approach to achieve the best heat recovery as well as economical applicability in an existing pasteurized milk plant. The new economizer is designed to divide an exhaust gas into two portions flowing up on the left and right of the economizes passing across aligned banks of tubes and then flowing down and up again in an unmixed-triple pass fashion. The pressure drop and dew point temperature of corrosive acid depended on the fuel's type are also taken into account. Moreover, the mathematical models based on the energy equation in partial differential equations of two-dimensional initial value problems have been developed to simulate the performance of the newly designed economizer. The observation data prove that the designed economizer can achieve the heat recovery of the exhaust gas up to 57% with the average of 38% and can save the consumption of liquefied petroleum gas of about 13%.

This study seeks to expand the range of climates and conditions in which free cooling from an economizer can replace air conditioning power consumption in residential applications. To explore this issue, we first discretize a simple building model in space and in time. We then solve the associated energy and mass balances for the estimated hourly heating and cooling loads and humidity conditions with respect to an annual climate profile. We propose a forecast-based algorithm to control the rate of outdoor airflow brought in by an economizer, in response to the upcoming cooling load to be experienced by the interior airspace. The algorithm takes advantage of a range of acceptable temperatures for thermal comfort by precooling the envelope overnight to delay the onset of cooling demand during the day. In order to consider the highest potential benefit from such an algorithm, we bypass the considerable problem of forecast accuracy by basing the inputs on the upcoming cooling load according to an initial simulation of the full year. On the whole, even with the forecast-based control, the results of the study have much in common with previous findings in the literature. Precooling works better to reduce cooling load in cases of higher thermal and moisture mass, but a humid climate severely restricts when free cooling is beneficial. For the example house considered here with the Austin climate and other assumptions, the effect of the proposed forecast-based economizer control was to greatly reduce the indoor air cooling load while greatly increasing the number of annual hours of unacceptably high indoor humidity. When we adjusted the forecast-based algorithm to avoid the excess humidity, the remaining reduction in cooling load was not significant. To investigate further how a forecast-based economizer could reduce cooling load in humid climates, the prinicipal task should be to extend the control algorithm to forecast and manage upcoming indoor humidity levels in the same fashion as was done in this study for indoor air temperature. / text

De nos, jours avec la démocratisation des équipements électroniques et l’explosions des services informatiques proposés sur le web, la consommation des datacenters devient un enjeu énergétique et économique majeur. Ce terme qui peut être traduit par « centre de calcul », désigne les infrastructures qui hébergent et font fonctionner en permanence des serveurs informatiques. Son rôle est de fournir aux équipements électroniques un environnement thermique adapté, ainsi qu’une alimentation électrique stable de manière à assurer une très grande sécurité de fonctionnement. Mais l’activité permanente des serveurs génère de grandes quantités de chaleurs, et un refroidissement permanent est nécessaire. Cette étude à pour objectif de mieux comprendre les phénomènes physiques qui interviennent dans le fonctionnement des datacenters afin d’apporter des solutions pour optimiser leur fonctionnement et diminuer leur consommation. A l’aide de simulations numériques, nous étudions les écoulements d’air et les transferts de chaleur qui interviennent dans la salle informatique, et nous proposons un nouveau modèle numérique qui permet de simuler le comportement des serveurs de nouvelle génération. Puis, grâce à une méthode de type POD, couplée au logiciel TRNSYS, nous développons un modèle « transversal » capable de simuler le fonctionnement complet d’un centre de calcul depuis les équipements informatiques, jusqu’au système de production d’air froid. Finalement, ce dernier est employé pour concevoir et tester un système de régulation adaptatif qui permet de réduire significativement les consommations d’énergie. / Nowadays, with the constant evolution of Information Technology (IT) equipments, the energy consumption of datacenter over the world becomes a major concern. These infrastructures are designed to provide an adapted thermal environment and an uninterrupted power supply to the IT servers, in order to guarantee a high level of reliability. However, the constant activity of electronic equipments releases a large amount of heat, and requires a constant cooling. Thus the objective of this work is to study the physical phenomena involved in an operating datacenter, in order to optimize the process and to reduce its energy consumption. Using numerical simulation, we study the air flow and the heat transfers happening in the servers’ room. To quantify the impact of new generation servers on the cooling process, we propose a numerical model that simulates the behavior of “blade” server. Then, using a Proper Orthogonal Decomposition (POD) method linked to the software TRNSYS, we propose a new “transversal” model, that simulates a datacenter behavior from the servers to the cooling plant. This model is used to develop a new adaptive regulation strategy, which constantly optimizes the system in order to ensure a safe thermal environment, and provides large energy savings.

In this thesis an apparatus is designed which enables the testing of thermal power plant boiler tubes against erosion. The apparatus makes use of a tube sample directly cut from the boiler tubes and simulates conditions similar to those prevailing in boilers in lignite fired power plants. The apparatus is composed of three components / a furnace for heating the sample, a loading system which allows application of tensile stresses while allowing the rotation of the sample, and a particle blower that delivers abrasive particles to the surface of the sample. The abrasive material used in the test is mixture of oxides, 90% of which is Al2O3 and the average particle size is approximately 300 &micro / m. The unit as designed would allow testing of boiler tubes up to a temperature of 650 C, and particle velocity of up to 50 m/s. The apparatus as tested at room temperatures for four identical samples have yielded very similar erosion values based on measurement of weight loss. At elevated temperature, erosion could be measured by a thickness loss since the oxidation that occurs complicates the erosion measurement. Two economizer material / P235GH and 16Mo3 were tested at 500oC with particle velocity of 10 m/s. The testing has shown that 16Mo3 has better performance than P235GH, the erosion rate differing by 20 percent.

The purpose of this Diploma Thesis was the construction design of the steam boiler for fytomass. For the specified parameters of biomass have been gradually implemented stoichiometric calculations of which are further based calculation of enthalpies of combustion gas. In the next part have been dealt with heat balance of the boiler, the efficiency of the boiler, recirculation of exhaust gases and the temperature of the combustion gases in outlet from fire. Thereinafter, the proposal of particular heat surfaces of steam boiler was solved, so that the resulting number and size correspond to the desired parameters. The parameters are temperature, pressure and the amount of steam.

Viktor Lípa Stillage boiler Graduation theses, power department, 2008 This graduation theses deals with designer solution of the boiler, include the dimensioning heat exchangers and engineering designer of the economizer chamber. Boiler is used for stillage combustion and fitted by natural circulation in vaporizer and stoker fired furnace.

The aim of this diploma thesis is the construction design of the steam boiler burning pellets. Set parameters: 450°C; 5,2 MPa; 30t/h. Decision procedure: stoichiometric calculation, energy balance, calculation of combustion chamber and heat delivery surface.

This thesis deals with the calculation of the boiler on stillage. Nowadays, when there's fossil fuels are just biomass seems adequate compensation. The great advantage of biomass boilers is a small amount of emissions, especially the greenhouse gas CO2. Of a given fuel composition is made thermal calculation and dimensioning of heat transfer surfaces of steam boilers. The resulting calculation must follow the parameters of steam at the outlet from the boiler.

To design a grate boiler with a natural circulation for burning of a pine bark with an output 18t/h is a primary objective of this dissertation. Individual parts of a boiler and it´s heat transfering surfaces were calculated after the working out of stoichiometric calculations from given element analysis of fuel. All computations have to fulfill several parameters: boliler output, temperature and pressure of an overheated steam.