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Air-to-air energy recovery wheels are now widely used in industry and buildings; however, the effectiveness of water vapor exchange in these regenerative wheels appears to be much lower than may be economically feasible. The purpose of this research is to investigate the feasibility of using agglomerated desiccant particle coatings to improve the performance of regenerative wheels used in HVAC air-to-air heat and moisture exchange and energy recovery applications. Desiccant particles coated on wheels lose most of their water vapor sorption capacity due to the method of coating. Desiccant agglomerates can be made by mixing starch, fine silica gel particulate, and water within an agglomerating device. The desiccant particle agglomerating process improves the desiccant mass transfer properties by increasing the overall surface area of desiccant particles; and also by creating a much rougher surface that can increase the likelihood of turbulent flow, and therefore, increasing the overall mass transfer rates. The industrial desiccant coating process involves submerging the desiccant into a coating agent and then applying this mix to the substrate or the matrix of the energy wheel. This process was improved in this research by ensuring the particles are applied after the coating agent is applied to ensure that the agglomerates or desiccant particles are not submerged by the coating material. Because testing energy wheels under steady state operating conditions has proved to be difficult, time consuming and costly in the past, a small parallel flow test cell is used to measure the transient response of coated substrate aluminum sheets after a step change in the inlet air humidity or temperature. Using a previously developed theoretical model, the time constants for these inlet step change responses are then used to predict the sensible and latent effectiveness of a regenerative energy wheel coated with the same agglomerated particles, which is rotated at a known operating speed and wheel face velocity. When the new desiccant coatings are used, it is shown that the latent heat effectiveness for a typical wheel could be up to 85%. It is found that the steady state air flow pressure drop readings for the test cell shows that agglomerated particles coated on the surfaces within the test cell implies some transitional turbulent flow behavior compared to similar substrate surfaces coated in a conventional manner with desiccant particles (e.g. up to 60% higher pressure drop at a channel Reynolds number of 300) in the same test cell. This implied enhanced turbulence flow friction factor in the test cell suggests a somewhat similar enhancement for increased mass and heat transfer coefficients for the test cell or coated wheel matrices. The transient results for humidity step changes for air flow through the test cell reveals that the adsorption and desorption response time constants are much larger for the agglomerated coated substrate surfaces than the conventional industrial coated surfaces. These data imply much higher moisture or latent heat effectiveness values for wheels coated with agglomerated particles. When the new desiccant coatings are used, it is shown that the latent heat effectiveness for a typical wheel could be better than 80% or 20% higher than currently available typical energy wheels. With improvements to the desiccant particle agglomerating process, desiccant coating process and particle coating and testing methods, this thesis shows that significant improvements may be practical for the design, testing and operation of regenerative heat and moisture exchange wheels.

Energy recovery ventilation (ERV) systems are designed to decrease the energy consumed by building HVAC systems. ERV’s scavenge sensible and latent energy from the exhaust air leaving a building or space and recycle this energy content to pre-condition the entering outdoor air. A few studies found in the open literature are dedicated to developing detailed numerical models to predict or simulate the performance of energy recovery wheels and desiccant wheels. However, the models are often computationally intensive, requiring a lot of time to perform parametric studies. For example, if the physical characteristics of a study target change (e.g., wheel diameter or depth) or if the system runs at different operating conditions (e.g., wheel rotation speed or airflow rate), the model parameters need to be recalculated. Hence, developing a mapping method with better computational efficiency, which will enable the opportunity to conduct extensive parametric or optimal design studies for different wheels is the goal of this research. In this work, finite difference method (FDM) numerical models of energy recovery wheels and desiccant wheels are established and validated with laboratory test results. The FDM models are then used to provide data for the development of performance mapping methods for an energy wheel or a desiccant wheel. After validating these new mapping approaches, they are employed using independent data sets from different laboratories and other sources available in the literature to identify their universality. One significant characteristic of the proposed mapping methods that makes the contribution unique is that once the models are trained, they can be used to predict performance for other wheels with different physical geometries or different operating conditions if the desiccant material is identical. The methods provide a computationally efficient performance prediction tool; therefore, they are ideal to integrate with transient building energy simulation software to conduct performance evaluations or optimizations of energy recovery/ desiccant wheel integrated HVAC systems.

Humans spend around 80 percent of their lifetime indoors. The humidity level plays an essential part in indoor climate, both in non-industrial applications, such as thermal comfort, and industrial ones. Dehumidification is a technology in the field of thermal comfort and indoor climate to control humidity levels. The need for the technology is essential for maintaining indoor humidity levels and lowering dew points. Based on the lack of studies that focus on the complete life cycle of the given dehumidification technology as well as the recently introduced EU Taxonomy there is an urgent need to evaluate the environmental impacts of the dehumidification systems. In this thesis, a comparative Life Cycle Assessment (LCA) is performed for two desiccant wheel dehumidifiers with industrial application driven fully by electric energy The intent of the LCA is to quantify the environmental performance of the two dehumidifier systems throughout their lifetime. The scope of this study is cradle-to-grave and includes four main life stages: cradle-to-gate, usage, maintenance and end-of-life. The objective is to identify the main drivers of selected environmental impact categories in each life phase and suggest areas of improvement. Seven categories are chosen based on the ReCiPe 2016 impact assessment method and that are related to the planetary boundaries. The two commonly available dehumidifiers will be analysed separately and in comparison. The functional unit used is 1 kg of water removed from the air which is independent of the performance of the system and focuses only on the wanted effect of humidity control. A base case is defined and scenarios are developed to cover different operational modes.  It is found that the usage stage which mainly consists of electricity demand contributes the most, varying between 65% and 99% of the overall impact in all categories. The cradle-to-gate stage, which shows the second biggest impact, has its most significant share in fine particulate matter formation, caused by the equipment for pre-treatment of air. Maintenance has the biggest variation depending on the scenario and application of the dehumidifiers where the number of maintenance occasions can vary significantly. This stage is however less crucial in the selected base case based on its small impact in most categories. End-of-life is insignificant for the results of this study having an average impact of less than 1%. The scenario analysis shows that a significant variation of the impact during usage is expected for different locations. This is mainly caused by the changing composition of the grid electricity which is identified overall main driver. The key parameters that influence the outcomes of this study are the operational hours of the systems, the target supply humidity as well as the climatic data. Potential for improvement is seen for an increased recycled content during the cradle-to-gate stage, the integration of sustainable energy technology as well as the connection of the systems to energy-efficient equipment during usage. Finally, it is concluded that an increase in material consumption may be tolerated by the systems if the energy performance is improved due to the dominating burden during the usage stage. The presented study may serve as example on how the EU Taxonomy can be applied within the field of dehumidification regarding environmental sustainability. It can also be used as a reference for further studies including the complete life cycle of dehumidifiers. Additional work may include other configurations of desiccant wheel dehumidifiers and extension to different assessment methods. / Människor spenderar cirka 80 procent av livet inomhus. Fuktighetsnivån är en viktig del av inomhusklimatet, både inom icke-industriella applikationer, såsom termisk komfort och industriella användningsområden. Avfuktning är en teknologi inom klimatkontroll inomhus och avlägsnar vattnet ur en luftström för att tillföra torr luft i rum. Den är väl ägnad om låga daggpunkter krävs. Möjliga användningsområden inom industrin är lagerutrymmen och förpackningsanläggningar, batteriproduktion, datacenter och farmaceutiska laboratorier. Denna studie har utförts eftersom det endast hittats ett fåtal studier som inkluderar hela livscykeln av sorptionsavfuktare. Utöver det så har EU taxonomin nyligen införts och den kan vara relevant för denna teknologi. Det finns därför ett behov att evaluera miljöpåverkan av dessa avfuktningssystem. I detta arbete utförs en jämförande livscykelanalys (LCA) av två rotorsorptionsavfuktare som används inom industrin och drivs av elektrisk energi. Meningen med denna LCA är att kvantifiera miljöpåverkan av de två systemen under hela livscykeln. Omfattningen av denna studie är ”från vaggan till graven” (eng. cradle-to-grave) och inkluderar fyra faser: tillverkning (eng. cradle-to-gate), användning, underhåll och demontering (eng. end-of-life). Syftet med arbetet är att kartlägga de centrala processer som driver miljöpåverkan, baserat på utvalda indikatorer och undersöka förbättringspotentialen. Sju kategorier från ReCiPe 2016 (som är en metod för miljökonsekvensbedömning) har valts ut för det baserat på de planetariska gränserna (eng. planetary boundaries). De två luftavfuktare analyseras enskilt och i jämförelse med varandra. Den funktionella enheten definieras som 1 kg vatten som tagits bort ur luften. Denna är oberoende av prestandan av systemet och beskriver endast avsedd effekt som är fuktighetskontroll. Utöver ett grundscenario har även olika scenarier utvecklats som beskriver varierande användning av avfuktaren.  Resultaten visar att användningen som mestadels består av elförbrukningen bidrar som mest till miljöpåverkan i alla kategorier med en andel mellan 65% och 99%. Tillverkningsfasen har näst störst påverkan av alla livsfaser och är mest relevant för fina partiklar. Detta orsakas av utrustningen för förbehandling av luften. Underhållet visar störst variation beroende på scenariot och användningen av avfuktaren eftersom antal underhållningstillfällen kan avvika mycket. Denna livsfas är däremot mindre relevant i grundscenariot eftersom den utgör endast en liten andel av den totala påverkan. Demontering är irrelevant för resultaten och utgör i genomsnitt mindre än 1%. Scenarioanalysen visar att en stor variation väntas för olika användningsställen eftersom produktionen av elen påverkar resultaten betydligt. De avgörande parametrar i denna studie är drifttimmar, målvärdet för fukthalten och klimatet. Förbättringspotential anses finnas i andelen återvunnet material i produktionsfasen, såsom integrering av hållbar energiteknik och energieffektiva lösningar under användningen. Det konstateras att en ökad konsumtion av material kan vara gynnsamt om detta reducerar påverkan under användningen. Detta är baserat på den tydliga skillnaden i påverkan under drift jämfört med de resterande livsfaser. Studien kan ses som exempel hur EU taxonomin för miljömässig hållbarhet skulle kunna appliceras inom avfuktning. Den kan också användas som referens för ytterligare studier inom området av livscykelanalys. Fortsatt arbete kan utökas till flera konfigurationer av rotorsorptionsavfuktare, såväl som inkluderandet av andra metoder för miljökonsekvensbedömning.