This  parametric study aims to predict the  performance of confluent jets ventilation (CJV) with variable air  volume (VAV) from four  CJV  design parameters. A  combination of  computational fluid dynamics (CFD), and response surface method (RSM) has  been used to  predict the  energy efficiency, thermal comfort and  IAQ  for  the  four  expected vital  design variables, i.e.,  heat load (XH),  number of  nozzles (XN),  airflow rate  (XQ) and  supply temperature (XTS).  The  RSM was  used to  generate a  quad-ratic  equation for  the  response variables exhaust temperature (TE),  sup-ply  temperature (TP),  PMV, DR, eT and  ACE. The  RSM  shows that  the  TE, TP and PMV were independent of the number of nozzles. The proposed equations were used to  generate setpoints optimized for  thermal com-fort  (PMV) for  summer, spring and  winter cases with different CLO  fac-tors  and  different TS under a  scenario where the  heat load varied between 10-30W/m2.  TE was  used as  setpoint to  regulate the  airflow rate  to  keep the  PMV values close to  zero. The  results show that  by adapting the TS to the CLO factor both thermal comfort and the energy efficiency can  be  improved. Further energy reduction can  be  gained by downregulating the airflow rate to keep the TP at a fixed setpoint when the  heat load is  decreased. This  means that  a  CJV  can  effectively be combined with VAV  to  improve environmental performance with good thermal comfort (-0.5<PMV <0.5,  DR <20%), above average IAQ (ACE = 106%) and  with a  higher heat removal efficiency (eT = 110%) than conventional mixing ventilation

In our digitalized world, Data Centers (DCs) serve as crucial infrastructure. Within the DC sector, data processing operations, including processes such as process cooling, hold special significance when investigated from an energy efficiency perspective, as they account for a substantial portion of total energy end-use. Therefore, it is important to prioritize data processing operations in energy management. The objective of this research is to explore the application of AI-powered clustering techniques to identify cooling operational statuses. Additionally, this research offers valuable perspectives on using AI for visualizing and identifying cooling patterns that deviate, which can provide valuable insights into DC energy management. The study object consists of a DC room equipped with Liquid Cooling Packages (LCPs). The findings show that the cooling power density on average is 9.1 kW/m 2 . Through analysis of the elbow curve, the optimal number of clusters is identified to be three. One of the identified clusters, i.e., Cluster 3, is characterized by large time periods with no supplied cooling from the LCPs. When comparing Clusters 1 and 2, Cluster 1 has a higher temperature difference between the chilled water supply and return, but a lower LCP return temperature compared to Cluster 2. Moreover, the quantified cooling characteristics contribute to the understanding of the LCPs’ operational statuses and cooling performance, which is useful for implementing targeted improvements, e.g., adjusting PID parameters, in the cooling infrastructure.

Soil-working tools in agriculture are made of boron-containing steels with high wear resistance and hardenability. Nevertheless, these tools are subject to high impacts, abrasive wear, and fatigue and are therefore prone to failure. To combine varying levels of properties within one component in as-quenched condition can be beneficial for such products. To obtain this property variation, a component must undergo a complex and controllable cooling. Therefore, the aim of this work is to obtain a microstructure gradient along two 15 mm-thick steel plates in a newly developed test rig by water jet impingement technique to confirm its controllability and flexibility. Furthermore, a quenching simulation model is created for hardness prediction using phase transformation data from a machine learning tool. Microstructure variation is observed using light optical microscopy and the electron backscatter diffraction technique. Mechanical properties are studied through tensile tests and hardness measurements and are also compared with simulation results. The 0.27 mass% C steel sample is obtained in almost fully martensitic state transitioning to a softer ferritic/bainitic condition, while the 0.38 mass% C steel sample results predominantly into a fully hardened martensitic state and slightly shows ferritic and bainitic features along the sample. The quenching simulation model shows promising hardness prediction for both steels.

Insulating building envelopes is crucial for maintaining indoor thermal comfort, particularlyin large-space enclosures like greenhouses having transparent envelopes. Transparent envelopesallow natural light but challenge temperature regulation due to their low thermal mass and highU-values, which enable significant heat transfer between indoor and outdoor environments. This fieldstudy aims to experimentally investigate whether warm wall confluent jets (WCJs) can maintain therequired indoor climate conditions in a greenhouse exposed to dynamic meteorological conditions inwinter. It analyzed the impact of the airflow rate, number of nozzle rows, and room air temperaturesetpoint on WCJ heating performance on the ceiling, external wall, and room air. Measurementswere performed with thermocouples and constant current anemometers, and the response surfacemethodology evaluated the effect of design variables on WCJ flow, thermal behavior, and the indoorenvironment. The results show that WCJs provided recommended air velocities and temperaturesindoors, with the airflow rate having the strongest effect on flow and thermal behavior, while thenumber of nozzle rows had a moderate effect. This study developed response surface models relatedto room air temperature, ceiling surface temperature, external wall temperature, and supply airtemperature. Supply temperatures between 27 ◦C and 40 ◦C suggest using low-exergy heat sources,like industrial waste heat, to sustain greenhouse operations during winter.

Direct Air Capture (DAC) technologies have emerged as a promising solution to address climate change and meet global climate goals. However, despite the importance of DAC in designing carbon-negative buildings, there is a lack of research focusing on the energy and cost aspects in building ventilation systems. The objective of this research is to investigate the CO2 capture potential and economic viability of integrating small-scale DAC into a building ventilation system integrated within a gym space. A gym space located in the city of Linköping, Sweden, is used as the research object. Furthermore, the study investigates the CO2 capture potential across a portfolio of gym spaces corresponding to an area of 24,760 m2. The results show that the CO2 capture potential varies between 54 kg/day and 83 kg/day for the investigated gym space. Moreover, the total CO2 capture potential is between 588 ton CO2/year and 750 ton CO2/year for the portfolio of gym spaces. The results also demonstrate that regenerating the sorbent during non-operating hours is more energy-efficient and economically advantageous compared to performing four complete regeneration cycles during operating hours. Based on a sorbent capture potential of 0.2 mmol/g and 2.0 mmol/g, and a CO2 price of 1,000 SEK, the break-even price for energy is 0.25–0.53 SEK/kWh. Lastly, the research shows that, among the investigated cases, the only economically viable solution corresponds to sorbent capture potential 2.0 mmol/g and utilizing low-grade heat for the generation process, resulting in a total cost of 663 SEK/ton CO2.

Hardening of carbon steel products by austenitization and immersion in a quenching medium is a widely used heat treatment to obtain a hard and strong martensitic structure. To avoid the undesired consequences, such as residual stresses or insufficient hardening depth, the cooling rates must be accurately measured and controlled. This can be achieved using the impinging water jet quenching technique. The aim of this work is to perform hardening of four low-alloyed 70 mm cylindrical carbon steel bars, using impinging water jet quenching technique with different jet flow rates, and to analyze its effect on thermal evolution and residual stresses. The temperature evolution during quenching experiments is recorded and used as input to a comprehensive quenching model to predict phase transformations, final hardness, and residual stresses of cylindrical bars. All four quenching experiments result in a fully hardened martensitic state. Furthermore, a decrease in jets’ flow rate, within a certain interval, results in different thermal histories and in lower compressive residual stresses on the surface. The results from quenching simulations show promising hardness, microstructure, and residual stress predictions that are validated by hardness measurements, optical microscopy, and residual stress analysis using X-Ray diffraction method.

The findings of this study demonstrate the potentialities in using the K-means algorithm for grouping data points related to cooling variables of LCP units. Additionally, the results show that it is suitable to divide the data points into four clusters. The identified clusters differ with regards to variables, among other, such as LCP return air temperature and temperature difference between chilled water supply and return. This is beneficial in identifying undesired operational statuses of LCPs, e.g., low temperature difference between chilled water supply and return, which is an indicator of a poor cooling performance. Clusters 1 is characterized by a combination of low LCP return air temperature and low average cooling power, which can be attributed to nonoperational periods during large parts of the analyzed time period. Cluster 2 has moderate LCP return air temperature, relatively low chilled water flow rate, and high △Tchilled water. In contrast, Cluster 3 demonstrates high chilled water flow rate and LCP return air temperatures, with relatively low △Tchilled water. Finally, Cluster 4 is featured by high LCP return air temperature, rather high △Tchilled water, and chilled water flow rate. It should be highlighted that in the context of energy efficiency, it is preferable to have a high △Tchilled water, and a low chilled water flow rate, meaning that Cluster 4 is preferred compared to Cluster 3.

With regards to the use of K-means as method in this research, it enhances data visualization and aids in deeper understanding of complex patterns within a dataset. Consequently, K-means can be used as a tool for data-driven analysis of cooling patterns in ICT rooms. Within the context of this research project, the use of K-means has been key for communication of results to facility management consultants and employees at Ericsson AB. Hence, undesired cooling patterns that deviate from the desired ones can be effectively communicated. Moreover, it is important to address the selection of four clusters, instead of three clusters, which were also considered suitable as previously mentioned. The motivation for this is to obtain a more detailed and comprehensive representation of the cooling characteristics in the dataset. As a result, this allows for a more granular depiction of the cooling patterns in the investigated dataset.

This report summaries the work within the project ”Effect of spatial-temporal behavior of a newly developed cooling system on carbon and stainless-steel bar properties”. The project was conducted from 2020-01-01 to 2022-12-31 and was co-produced by SSAB, Outokumpu and University of Gävle (UoG). The Knowledge Foundation, SSAB, Outokumpu and UoG financed the project.

For the Swedish steel companies SSAB and Outokumpu producing special steels, it is very important to be able to control the cooling process in order to produce steel bars with excellent properties. Both steel companies also want to be able to control the cooling process so that the excellent steel properties become even over the bars’ spatial configuration.

The aim of the present project is to reveal the spatial-temporal behavior of a newly developed cooling technology in order to produce steel bars with excellent properties and to control the phase transformation to achieve optimal performance of the steel bars.

By using the special test rig at the UoG, detail temperature measurement mapping, invers solution and direct numerical simulation, the present project has identified and quantified several important aspects related to the quenching process, operating conditions, and temperature field development within the investigated products. The result from the proposed cooling process provides an outstanding cooling rate that is very crucial to obtain the required steel phase and thus the correct properties of the bar with different sizes. Results from this study have also shown that the cost per kg product can be reduced by tunning the process parameters such as soaking time and bar temperature before starting the cooling process.

In addition, both experimental and numerical results of the material investigation show that the cooling technology has resulted in the desired phase transformation and subsequently the desired steel phases and material properties. The results show that the cooling technology and the control of the cooling parameters can be used to optimize the material properties of the bar materials.

These good results and conclusions have been obtained via the deep collaboration between the SSAB, Outokumpu and UoG. The co-production, starting in the steering group planning the work along with the combination of research conducted at UoG and at the companies, have led to a successful project with great knowledge transfer in all direction during the duration of the project.

Den globala efterfrågan på mat förväntas öka avsevärt i framtiden, driven av faktorer såsom befolkningsökning och industriell utveckling. Dessutom har vikten av en robust livsmedelsförsörjning nationellt fått ökad uppmärksamhet med tanke på globala klimatförändringar och politiska konflikter. Matproduktion i klimatstyrda växthus erbjuder lovande möjligheter för att möta den ökande efterfrågan på prisvärda och hållbara livsmedel. Trots de fördelar som är förknippade med matproduktion i växthus, står vi inför ett antal utmaningar som behöver hanteras, särskilt i ett land med kallt klimat som Sverige. Detta inkluderar låga utomhustemperaturer, begränsad solinstrålning, samt höga energikostnader för att upprätthålla ett gynnsamt odlingsklimat. 

I föreliggande studie undersöker vi potential med Wall Confluent Jet (WCJ) för att skapa och upprätthålla en gynnsam inomhusmiljö för grödodling i ett växthusklimat. Fördelarna med WCJ inkluderar bland annat användandet av lågtemperarad industriell spillvärme, utebliven risk för kondens, samt tillförsel av önskvärda nivåer av luftfuktighet och CO2.  Dessutom syftar arbetet till att studera den teknoekonomiska prestandan hos WCJ i jämförelse med konventionell uppvärmning via fjärrvärme. Arbetet är uppdelat i två delar: (1) fältexperiment med mätningar av luft- och yttemperaturer för att studera prestandan i WCJ, och (2) teknoekonomisk analys som inkluderar olika klimatzoner, fjärrvärmepriser, samt olika priser på lågtempererad industriell spillvärme. Ett växthus, med ett integrerar testrum, som är beläget i Hofors används som fallstudie. 

Resultaten visar att WCJ-tekniken levererar en jämn och relativt konstant termisk miljö, samt att WCJ klistras vid både tak- och bakväggens ytor och därmed värmer upp dessa ytor. Vidare, den genomsnittliga energianvändningen för uppvärmning minskar från 381 kWh/m2∙år utan WCJ-teknik till 167 kWh/m2∙år med WCJ (56% minskning). WCJ-tekniken möjliggör också en genomsnittlig minskning av energikostnaderna från 441 kSEK/år till 43 kSEK (>90%).  Detta är kopplat till signifikant lägre energianvändning med WCJ, och betydligt lägre priser för lågtempererad industriell spillvärme jämfört med lokala fjärrvärmepriser för de analyserade klimatzonerna. 

The global demand for food is expected to increase significantly in the future, driven by factors such as population growth and industrial development. Additionally, the importance of a robust national food supply has gained increased attention in light of global climate change and political conflicts. Environmentally controlled greenhouse food production offers promising opportunities to meet the growing demand for affordable and sustainable food. However, there are several challenges that need to be addressed, particularly in countries with cold climates like Sweden. These challenges include low outdoor temperatures, limited solar radiation, and high energy costs to maintain desirable greenhouse indoor conditions.

In this study, we explore the potential of the Wall Confluent Jet (WCJ) technology to create and maintain a favorable indoor environment for crop cultivation in a greenhouse setting. The advantages of WCJ include the utilization of low-temperature industrial waste heat, no risk for condensation, and the supply of desired levels of humidity and CO2. Furthermore, the study aims to assess the techno-economic performance of WCJ compared to conventional district heating for heating of greenhouses. The study is divided into two parts: (1) field experiments with measurements of air and surface temperatures to study the performance of the WCJ, and (2) techno-economic analysis considering different climate zones, district heating prices, and variations in prices of low-temperature industrial waste heat. A greenhouse with an integrated lab room located in Hofors is used as a case study.

The results demonstrate that the WCJ technology provides a consistent and relatively stable thermal environment, with WCJ adhering to both the ceiling and back wall surfaces, thereby heating these surfaces. Furthermore, the average energy use for heating decreases from 381 kWh/m2∙year without WCJ technology to 167 kWh/m2∙year with WCJ (a 56% decrease). The WCJ technology also enables an average decrease in energy costs from 441 kSEK/year to 43 kSEK/year (>90%). This is attributed to significantly lower energy use with WCJ and considerably lower prices for low-temperature industrial waste heat compared to local district heating prices in the studied climate zones. 

The study aimed to explore the effects of inlet air temperature, outdoor air temperature, inlet bulk velocity, and the number of nozzles on wall confluent jets (WCJ) propagating along an external cold wall in a large space enclosure such as a greenhouse. A combination of experimental study and Response surface methodology has been used to predict the flow and thermal behavior of the WCJ for the studied cases. Box-Behnken design was used to determine the case matrix for four of the above-mentioned vital variables for non-isothermal cases. The experimental study employed constant current anemometers to measure the velocity and temperature of the WCJ. Results showed that the WCJ attached to the wall under both isothermal and non-isothermal conditions. This flow behavior suggests that the WCJ can be used to heat the external facades of large-space enclosures. All the stated variables were critical to the decay factor and decay rate of maximum velocity, albeit at varying levels. The velocity decayed faster with an increase in the inlet bulk velocity and outdoor air temperature. It also decayed faster as the number of nozzles and inlet air temperature decreased. The external wall surface temperature and the wall-heating effect increased as the momentum of the jet increased. The surface temperature on the external wall was most influenced by the inlet air temperature and least by the number of nozzles. Correlations of the second-order polynomial for the Response surface models that estimate the rate of velocity decay and temperature on the external wall were obtained.