scholarly journals Theoretical Analysis of Vuilleumier’s Hypothetical Engine and Cooler

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5923
Author(s):  
Qi Liu ◽  
Baojun Luo ◽  
Jiayao Yang ◽  
Qun Gao ◽  
Jingping Liu ◽  
...  
Keyword(s):  
Heat Flow ◽  
Theoretical Analysis ◽  
Power Flow ◽  
Cold Temperature ◽  
Warm Temperature ◽  
Promising Technology ◽  
Hot Temperature

Vuilleumier machines are a promising technology for heating. Respective performances of Vuilleumier’s engine and cooler are generally unclear. In Stirling machines, performances can be determined based on PV power flow and heat flow methods. In this work, respective performances based on two methods in current Vuilleumier models were investigated. It was found that PV power flow and heat flow methods in current Vuilleumier models were ineffective for analysis of respective performances due to there being no piston as a boundary between Vuilleumier’s engine and cooler. Then, a virtual piston was assumed, and a virtual piston based Vuilleumier model (VPBVM) was developed. The relative Carnot efficiencies of the obtained engine and cooler were 53~64% and 43~49%, respectively, at conditions of 550 °C hot temperature, 50~70 °C warm temperature, and −20~10 °C cold temperature. The results indicated that respective performances obtained in VPBVM were reasonable. Moreover, the engine’s compression ratios could be obtained in VPBVM and were 1.2~1.24. Thus, VPBVM could be effective for the analysis of the Vuilleumier machine’s engine and cooler.

scholarly journals Spatiotemporal Variability and Trends in Extreme Temperature Events in Finland over the Recent Decades: Influence of Northern Hemisphere Teleconnection Patterns

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Masoud Irannezhad ◽  
Hamid Moradkhani ◽  
Bjørn Kløve
Keyword(s):  
Northern Hemisphere ◽  
Extreme Temperature ◽  
Cold Temperature ◽  
Spatiotemporal Variability ◽  
The Arctic ◽  
Temperature Extremes ◽  
Warm Temperature ◽  
Teleconnection Patterns ◽  
The North ◽  
Temperature Indices

Fifteen temperature indices recommended by the ETCCDI (Expert Team on Climate Change Detection and Indices) were applied to evaluate spatiotemporal variability and trends in annual intensity, frequency, and duration of extreme temperature statistics in Finland during 1961–2011. Statistically significant relationships between these high-resolution (10 km) temperature indices and seven influential Northern Hemisphere teleconnection patterns (NHTPs) for the interannual climate variability were also identified. During the study period (1961–2011), warming trends in extreme temperatures were generally manifested by statistically significant increases in cold temperature extremes rather than in the warm temperature extremes. As expected, warm days and nights became more frequent, while fewer cold days and nights occurred. The frequency of frost and icing days also decreased. Finland experienced more (less) frequent warm (cold) temperature extremes over the past few decades. Interestingly, significant lengthening in cold spells was observed over the upper part of northern Finland, while no clear changes are found in warm spells. Interannual variations in the temperature indices were significantly associated with a number of NHTPs. In general, warm temperature extremes show significant correlations with the East Atlantic and the Scandinavia patterns and cold temperature extremes with the Arctic Oscillation and the North Atlantic Oscillation patterns.

scholarly journals Soft-Switching High Gain Step-Up DC/DC Converter without Auxiliary Switches

2019 ◽  
Vol 8 (12S) ◽  
pp. 633-636
Keyword(s):  
Theoretical Analysis ◽  
Power Flow ◽  
High Efficiency ◽  
Input Voltage ◽  
High Gain ◽  
Soft Switching ◽  
Zero Voltage Switching ◽  
Auxiliary Cell ◽  
Zero Voltage ◽  
Voltage Switching

This manuscript presents a novel high gain, high efficiency Soft-switching high step-up DC/DC converter for battery-operated vehicles. The high step-up converter can transfer the power flow from the small voltage to high voltage. The conventional two input inductor hard switched non-isolated DC-DC converter improved with an additional auxiliary cell to attain the Zero voltage switching, due to obtaining the softswitching the efficiency may improve and reduces the stress across the main switches. The isolated converters are used as a transformer to attain high gain, whereas in the proposed converter obtains the high gain without a transformer and contains the high efficiency in the step-up mode of operation. The main aim of the converter is to attain the Zero voltage switching without using any additional auxiliary switches. In this paper, the input voltage applied as 30V, and the obtained output voltage is fifteen times to the applied voltage, which is 450V and the output power 850W. This paper mainly presents the theoretical analysis of converter operation and the evaluation of the simulation results validated with the theoretical analysis.

A Theoretical Analysis of Heat Flow in Reverse Combustion

1960 ◽  
Vol 219 (01) ◽  
pp. 124-131 ◽  
Author(s):  
V.J. Berry ◽  
D.R. Parrish
Keyword(s):  
Heat Flow ◽  
Theoretical Analysis

Small to large scale mixed turbulent convection: buildings application

2018 ◽  
Vol 28 (1) ◽  
pp. 188-205 ◽  
Author(s):  
Souad Morsli ◽  
Mustapha Boussoufi ◽  
Amina Sabeur ◽  
Mohammed El Ganaoui ◽  
Rachid Bennacer
Keyword(s):  
Flow Structure ◽  
Large Scale ◽  
Natural Ventilation ◽  
Vertical Wall ◽  
Cold Temperature ◽  
Temperate Climate ◽  
3D Flow ◽  
Content Type ◽  
Hot Temperature ◽  
The One

Purpose The use of natural ventilation by large openings to maintain thermal comfort conditions in the premises is a concept that is perfectly integrated into the traditional architecture of countries in the Mediterranean region or in tropical climates. In a temperate climate where the architecture is not usually designed to respond to the use of natural ventilation is seasonal and is done at the initiative of the occupants by making changes in the design of their doors. The European interest in natural ventilation, as a passive building air-conditioning technology, is increasing and has been the subject of a research program commissioned by the European Community. In this work, the authors consider a part of a housing compound as a refreshing floor. This floor is maintained at a constant cold temperature, the one vertical wall at hot temperature and other surfaces are adiabatic. Various scenarios are considered for this work. Mixed convection for different boundary conditions and different configurations is carried out. In addition, an airflow is injected through a window and extracted on the opposite window. Classical conclusion and transitional value on Richardson number have been completed by the new thermal configuration with nonsymmetric thermal conditions. The complex 3D flow structure is more obvious when one of the two flows (ventilation or natural convection) dominates. However, the induced heat transfer is less sensitive to the added ventilation. In this study, the authors consider a part of a housing compound as a refreshing floor. This floor is maintained at a constant cold temperature, the one vertical wall at hot temperature and other surfaces are adiabatic. Design/methodology/approach This is a qualitative preliminary study of a 2D–3D flow. The authors examine the competition between the natural convective flow and the added airflow on the flow structure and indoor air quality. The numerical model shows a good agreement with that obtained by researchers analytically and experimentally. To deal with turbulence, the RNG k-ε model has been adopted in this study. Findings The transfer is more sensitive between the 2D and 3D cases for the present analyzed case. Originality/value The study of ventilation efficiency has shown the competition between the big and small structures and the induced discomfort.

scholarly journals Decreased noise figure measurement uncertainty in <i>Y</i> factor method

2013 ◽  
Vol 11 ◽  
pp. 1-5
Author(s):  
I. Gaspard
Keyword(s):  
Measurement Uncertainty ◽  
Noise Source ◽  
Noise Figure ◽  
Cold Temperature ◽  
Excess Noise ◽  
Noise Power ◽  
Noise Sources ◽  
Hot Temperature ◽  
Factor Method ◽  
Equivalent Noise Power

Abstract. Almost always noise figure is measured today by using a matched noise source delivering two different but known noise temperatures (Y factor method). In commercially available noise sources these temperatures are characterized by the excess noise ratio (ENR) value, describing the ratio of equivalent noise power when switched on related to the noise power of a resistor at a temperature of 290 K (switched off). For a typical ENR value of 5 dB that means a hot temperature Th=1207 K and a cold temperature Tc = 290 K.

Phononics: A New Science and Technology of Controlling Heat Flow and Processing Information by Phonons

2010 ◽  
Author(s):  
Lei Wang ◽  
Gang Zhang ◽  
Gang Wu ◽  
Nuo Yang ◽  
Baowen Li
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Information Processing ◽  
Heat Flow ◽  
Theoretical Analysis ◽  
Lattice Vibration ◽  
Logic Gate ◽  
New Science ◽  
Processing Information ◽  
Experimental Works

Heat due to lattice vibration (phonons) is traditionally regarded as harmful for information processing. In this paper, we will demonstrate via numerical simulation, theoretical analysis and experiments that, phonons, can be manipulated like electrons. They can be used to carry and process information. Basic phononic devices such as thermal diode, thermal transistor, thermal logic gate and thermal memory will be discussed via nonlinear lattice model. Moreover, we will also discuss how to manipulate and tune thermal conductivity of nanostructure so that to control heat flow. Both theoretical and experimental works will be shown.

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