Low energy cooling for buildings in central Europe - case studies

The paper deals with applicability of passive and low energy cooling technologies in the Czech Republic. In the paper there are presented two recent studies, where computer simulation helps to design properly the passive and low energy cooling for buildings is the Czech Republic. There is presented case studies applying, night cooling, thermal mass and slab cooling. The role of computer simulation in the low energy building design and optimalization is discussed

Computer simulation for better design and operation of large office building air-conditioning

The paper deals with the use of computer simulations both for the design support of a new buildings and HVAC system development and for the optimisation of the system control strategy in the building. This is presented on a real office building in Prague. For a new large bank head office in Prague, computer simulations were carried out to find solutions for reducing the required cooling capacity, verify the fan-coil capacity design, and optimise the external gassing for atriums. Because the design included exposed concrete ceilings, the idea was to apply building thermal mass and find out a way to operate the building. The cooling capacity was initially estimated at 3 MW and simulations proved possibility of decreasing it to 81% for the whole building. Other simulation helped designers to optimise, roof glazing and shading for atria, with stress on thermal comfort in open corridors. The building and HVAC system monitoring and meassurements to confirm the simulation based design changes are presented in the paper

Low energy cooling of buildings in central Europe - case studies

This paper addresses the applicability of passive and low energy cooling technologies in the Czech Republic. The main research methods are climate analysis and buildings and systems analysis, both with the objective to assess the building performance potential of passive and low energy cooling technologies. The analysis is based on case studies, which include building performance simulation as well as in-situ monitoring. The role of computer simulation in low energy building design and optimisation is briefly discussed

Simulation of a data center cooling system in an emergency situation

The paper deals with keeping server rooms at reasonable air temperature in the case of an electrical power failure in a data center and with building performance simulations used to support emergency power planning. An existing data center was analyzed in detail with respect to the possibilities of emergency cooling. Based on the assumption that the thermal capacity of already chilled water can be used to prolong functionality of the cooling system when the roof chillers are out of operation, a backup power supply was designed for Computer Room Air-Conditioning and even for the cooling liquid circuit pumps (i.e. not for the roof chillers). Special models representing the data center indoor environment and cooling system, including a detailed model of the Computer Room Air Conditioning (CRAC) units, were developed in order to estimate the time period during which the internal air temperatures in the server room will not exceed the limit. The numerical model of the server room and the cooling system was built in the TRNSYS software and calibrated by measured data acquired from a real power outage situation. The results and conclusions obtained from the performed analyses and simulations helped to improve the emergency power plan of the data center. The study also forms the basis for the development of an emergency decision algorithm that will included in the novel supervisory control platform: GENi

Simulation-based assessment of thermal aware computation of a bespoke data centre

The role of Data Centres (DCs) as global electricity consumers is growing rapidly due to the exponential increase of computational demand that modern times require. Control strategies that minimize energy consumption while guaranteeing optimal operation conditions in DC are essential to achieve sustainable and energy efficient DCs. Unfortunately, the development and testing of novel control strategies are often slowed down, if not discarded. This is generally due to the lack of access caused by safety and economic reasons. Alternatively, simulation experiments represent a “safe” virtual environment to test novel control strategies, accelerating the process for their implementation in physical DCs. The virtual DC testbed, originated in the GENiC project, supports the development and dynamic testing of control and energy management algorithms. This paper introduces its features and describes its functionality through a simulation-based assessment of thermal aware computation strategy. For this, the virtual DC will be based on a bespoke DC located in Cork (Ireland). This DC has 30 kW capacity, 40 m2 floor area and its layout follows a hot aisle - cold aisle arrangement without containment. The performance the IT Workload allocation under different scenarios and their influence both on the whitespace environment and overall DC performance are evaluated and quantified. Finally, the benefits of a coordinated operation between the thermal and the IT workload managements are discussed

Computer simulation for better air-conditioning and ventilation design of industrial halls

The paper deals with the use of computer simulations both for the design support of HVAC systems development in existing industrial buildings. There is presented selected industrial hall and its HVAC systems concept. The computer simulation using ESP-r software for different rates of ventilation by outdoor air helped to design an air-conditioning system, which comprises of daytime top cooling and night ventilation by outdoor air combined with accumulation of cold in building constructions. Capacity of mechanical cooling was decreased to more that 50% comparing to original design based on manual calculation for peak loads. The importance of internal gains measurements and investigation for industrial halls is presented as well

Biomechanical and physiological differences between synchronous and asynchronous low intensity handcycling during practice-based learning in able-bodied men

BACKGROUND: Originally, the cranks of a handcycle were mounted with a 180° phase shift (asynchronous). However, as handcycling became more popular, the crank mode switched to a parallel mounting (synchronous) over the years. Differences between both modes have been investigated, however, not into great detail for propulsion technique or practice effects. Our aim is to compare both crank modes from a biomechanical and physiological perspective, hence considering force and power production as a cause of physiological outcome measures. This is done within a practice protocol, as it is expected that motor learning takes place in the early stages of handcycling in novices. METHODS: Twelve able-bodied male novices volunteered to take part. The experiment consisted of a pre-test, three practice sessions and a post-test, which was subsequently repeated for both crank modes in a counterbalanced manner. In each session the participants handcycled for 3 × 4 minutes on a leveled motorized treadmill at 1.94 m/s. Inbetween sessions were 2 days of rest. 3D forces, handlebar and crank angle were measured on the left hand side. Kinematic markers were placed on the handcycle to monitor the movement on the treadmill. Lastly, breath-by-breath spirometry combined with heart-rate were continuously measured. The effects of crank mode and practice-based learning were analyzed using a two way repeated measures ANOVA, with synchronous vs asynchronous and pre-test vs post-test as within-subject factors. RESULTS: In the pre-test, asynchronous handcycling was less efficient than synchronous handcycling in terms of physiological strain, force production and timing. At the post-test, the metabolic costs were comparable for both modes. The force production was, also after practice, more efficient in the synchronous mode. External power production, crank rotation velocity and the distance travelled back and forwards on the treadmill suggest that asynchronous handcycling is more constant throughout the cycle. CONCLUSIONS: As the metabolic costs were reduced in the asynchronous mode, we would advise to include a practice period, when comparing both modes in scientific experiments. For handcycle users, we would currently advise a synchronous set-up for daily use, as the force production is more effective in the synchronous mode, even after practice

Role of strontium cations in ZSM-5 zeolite in the methanol-to-hydrocarbons reaction

The selectivity of the methanol-to-hydrocarbons (MTH) reaction can be tuned by modifying zeolite catalysts with alkaline earth metals, which typically increase propylene selectivity and catalyst stability. Here we employed Sr2+ as its higher atomic number in comparison to the zeolite T atoms facilitates characterization by scanning transmission electron microscopy and operando X-ray absorption spectroscopy. Sr2+ dispersed in the ZSM-5 micropores coordinates water, methanol, and dimethyl ether during the MTH reaction. Complementary characterization with nuclear magnetic resonance spectroscopy, thermogravimetric analysis combined with mass spectrometry, operando infrared spectroscopy, and X-ray diffraction points to the retention of substantially more adsorbates during the MTH reaction in comparison to Sr-free zeolites. Our findings support the notion that alkaline earth metals modify the porous reaction environment such that the olefin cycle is favored over the aromatic cycle in the MTH, explaining the increased propylene yield and lower deactivation rate