Boron cosmochemistry. Part II: Boron nucleosynthesis and condensation temperature

AbstractIn refrigeration systems, evaporative condensers have two main advantages compared to other condensation heat exchangers: They operate at lower condensation temperature than traditional air-cooled condensers and require a lower quantity of water and pumping power compared to evaporative towers. The heat and mass transfer that occur on tube batteries are difficult to study. The aim of this work is to apply an experimental approach to investigate the performance of an evaporative condenser on a reduced scale by means of a test bench, consisting of a transparent duct with a rectangular test section in which electric heaters, inside elliptical pipes (major axis 32 mm, minor axis 23 mm), simulate the presence of the refrigerant during condensation. By keeping the water conditions fixed and constant, the operating conditions of the air and the inclination of the heat transfer geometry were varied, and this allowed to carry out a sensitivity analysis, depending on some of the main parameters that influence the thermo-fluid dynamic phenomena, as well as a performance comparison. The results showed that the heat transfer increases with the tube surface exposed directly to the air as a result of the increase in their inclination, that has been varied in the range 0–20°. For the investigated conditions, the average increase, resulting by the inclination, is 28%.

Download Full-text

Performance Evaluation of an Adsorption Heat Pump System Using MSC-30/R1234yf Pair with the Impact of Thermal Masses

Applied Sciences ◽

10.3390/app11052279 ◽

2021 ◽

Vol 11 (5) ◽

pp. 2279

Author(s):

Sangwon Seo ◽

František Mikšík ◽

Yuta Maeshiro ◽

Kyaw Thu ◽

Takahiko Miyazaki

Keyword(s):

Heat Pump ◽

Adsorption Isotherms ◽

Coefficient Of Performance ◽

Variable Pressure ◽

Condensation Temperature ◽

Relative Pressure ◽

Pump System ◽

Adsorption Heat Pump ◽

Adsorbed Phase ◽

The Impact

In this study, we evaluated the performance of low Global Warming Potential (GWP) refrigerant R1234yf on the activated carbon (MSC-30) for adsorption heating applications. The adsorption isotherms of MSC-30/R1234yf were measured using a constant-volume–variable-pressure (CVVP) method from very low relative pressure to the practical operating ranges. The data were fitted with several isotherm models using non-linear curve fitting. An improved equilibrium model was employed to investigate the influence of dead thermal masses, i.e., the heat exchanger assembly and the non-adsorbing part of the adsorbent. The model employed the model for the isosteric heat of adsorption where the adsorbed phase volume was accounted for. The performance of the heat pump was compared with MSC-30/R134a pair using the data from the literature. The analysis covered the desorption temperature ranging from 60 °C to 90 °C, with the evaporation temperature at 5 °C and the adsorption temperature and condensation temperature set to 30 °C. It was observed that the adsorption isotherms of R1234yf on MSC-30 were relatively lower than those of R134a by approximately 12%. The coefficient of performance (COP) of the selected pair was found to vary from 0.03 to 0.35 depending on the heat source temperature. We demonstrated that due to lower latent heat, MSC-30/R1234yf pair exhibits slightly lower cycle performance compared to the MSC-30/R134a pair. However, the widespread adaptation of environmentally friendly R1234yf in automobile heat pump systems may call for the implementation of adsorption systems such as the direct hybridization using a single refrigerant. The isotherm and performance data presented in this work will be essential for such applications.

Download Full-text

Bose-Einstein condensation temperature of dipolar gas in anisotropic harmonic trap

Physical Review A ◽

10.1103/physreva.76.023604 ◽

2007 ◽

Vol 76 (2) ◽

Cited By ~ 19

Author(s):

K. Glaum ◽

A. Pelster

Keyword(s):

Harmonic Trap ◽

Einstein Condensation ◽

Condensation Temperature ◽

Bose Einstein Condensation ◽

Bose Einstein

Download Full-text

Dynamic Modelling and Experimental Validation of a Domestic Refrigeration Cycle

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4052453 ◽

2021 ◽

pp. 1-33

Author(s):

Akin Caglayan ◽

Salman Mustafa Husain ◽

Mutlu Ipek ◽

Tolga Nurettin Aynur ◽

Sertac Cadirci

Keyword(s):

Capillary Tube ◽

Dynamic Modelling ◽

Object Oriented Programming ◽

Condensation Temperature ◽

Refrigeration Cycle ◽

Transient Behaviour ◽

Analysis And Design ◽

Cyclic Behaviour ◽

Suction Line Heat Exchanger ◽

Tube Suction

Abstract Performance analysis and design optimization of refrigerators are primarily carried out by time-consuming experiments. The current study presents an alternative method of analysing refrigerators through modelling of the cooling cycle using a software called Dymola, based on an object-oriented programming language, called Modelica. The main components of a domestic refrigerator (compressor, condenser, evaporator, cabinet and capillary tube-suction-line heat exchanger) are first modelled and validated individually. The full dynamic refrigeration cycle model is created afterwards. Both the simulations and the experiments have been conducted using R600a as the refrigerant with on-and off-modes of the reciprocating, single speed compressor. To represent the dynamic cyclic behaviour of the refrigerator, an algorithm block is also included. The algorithm controls the operation using two set-point temperatures of the cabinet. Experiments have been carried out on a single door refrigerator having an interior volume of 343 litres for the validation of the one-dimensional dynamic model. Results show that the cabinet air, evaporation temperature, condensation temperature, power and energy values deviate from experimental values by less than 2°C and 2% respectively. The dynamic modelling is found to be in good agreement with the experiments in the on mode of the compressor and a promising and rapid tool to represent the transient behaviour of the refrigerator.

Download Full-text

Using non-solar-scaled opacities to derive stellar parameters

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833753 ◽

2018 ◽

Vol 620 ◽

pp. A54 ◽

Cited By ~ 4

Author(s):

C. Saffe ◽

M. Flores ◽

P. Miquelarena ◽

F. M. López ◽

M. Jaque Arancibia ◽

...

Keyword(s):

High Precision ◽

Chemical Species ◽

Model Atmosphere ◽

Condensation Temperature ◽

Spectroscopic Methods ◽

Fundamental Parameters ◽

Evolved Stars ◽

Solar Type ◽

Scaled Models ◽

Previous Step

Aims. In an effort to improve spectroscopic methods of stellar parameters determination, we implemented non-solar-scaled opacities in a simultaneous derivation of fundamental parameters and abundances. We wanted to compare the results with the usual solar-scaled method using a sample of solar-type and evolved stars. Methods. We carried out a high-precision determination of stellar parameters and abundances by applying non-solar-scaled opacities and model atmospheres. Our sample is composed of 20 stars, including main sequence and evolved objects. The stellar parameters were determined by imposing ionization and excitation equilibrium of Fe lines, with an updated version of the FUNDPAR program, together with plane-parallel ATLAS12 model atmospheres and the MOOG code. Opacities for an arbitrary composition and vmicro were calculated through the opacity sampling (OS) method. We used solar-scaled models in the first step, and then continued the process, but scaled to the abundance values found in the previous step (i.e. non-solar-scaled). The process finishes when the stellar parameters of one step are the same as in the previous step, i.e. we use a doubly iterated method. Results. We obtained a small difference in stellar parameters derived with non-solar-scaled opacities compared to classical solar-scaled models. The differences in Teff, log g, and [Fe/H] amount to 26 K, 0.05 dex, and 0.020 dex for the stars in our sample. These differences can be considered the first estimation of the error due to the use of classical solar-scaled opacities to derive stellar parameters with solar-type and evolved stars. We note that some chemical species could also show an individual variation greater than those of the [Fe/H] (up to ~0.03 dex) and varying from one species to another, obtaining a chemical pattern difference between the two methods. This means that condensation temperature Tc trends could also present a variation. We include an example showing that using non-solar-scaled opacities, the solution found with the classical solar-scaled method indeed cannot always verify the excitation and ionization balance conditions required for a model atmosphere. We discuss in the text the significance of the differences obtained when using solar-scaled versus non-solar-scaled methods. Conclusions. We consider that the use of the non-solar-scaled opacities is not mandatory in every statistical study with large samples of stars. However, for those high-precision works whose results depend on the mutual comparison of different chemical species (such as the analysis of condensation temperature Tc trends), we consider its application to be worthwhile. To date, this is probably one of the most precise spectroscopic methods for stellar parameter derivation.

Download Full-text

KAJI PERFORMANSI REFRIGERAN R-290, R-32, DAN R-410A SEBAGAI ALTERNATIF PENGGANTI R-22

ALE Proceeding ◽

10.30598/ale.4.2021.133-139 ◽

2021 ◽

Vol 4 ◽

pp. 133-139

Author(s):

Rikhard Ufie ◽

Cendy S. Tupamahu ◽

Sefnath J. E. Sarwuna ◽

Jufraet Frans

Keyword(s):

Air Conditioning ◽

Cooling Capacity ◽

Coefficient Of Performance ◽

Condensation Temperature ◽

Vapor Compression ◽

Know How ◽

Evaporation Temperature ◽

Vapor Compression Cycle ◽

Compression Cycle ◽

Refrigeration Capacity

Refrigerant R-22 is a substance that destroys the ozone layer, so that in the field of air conditioning it has begun to be replaced, among others with refrigerants R-32 and R-410a, and also R-290. Through this research, we want to know how much Coefficient of Performance (COP) and Refrigeration Capacity (Qe) can be produced for the four types of refrigerants. The study was carried out theoretically for the working conditions of the vapor compression cycle with an evaporation temperature (Tevap) of 0, -5, and -10oC, a further heated refrigerant temperature (ΔTSH) of 5 oC, a condensation temperature (Tkond) of 45 oC and a low-cold refrigerant temperature. (ΔTSC) 10 oC and compression power of 1 PK . The results of the study show that the Coefficient of Performance (COP) in the use of R-22 and R-290 is higher than the use of R-32 and R-410a, which are 4,920 respectively; 4,891; 4.690 and 4.409 when working at an evaporation temperature of 0 oC; 4.260; 4,234; 4.060 and 3.812 when working at an evaporation temperature of -5 oC; and amounted to 3,730; 3,685; 3,550 and 3,324 if working at an evaporation temperature of -10 oC. Based on the size of the COP, if this installation works with a compression power of 1 PK, then the cooling capacity of the R-22 and R-290 is higher than the R-32 and R-410a, which are 3,617 respectively. kW; 3,597 kW; 3,449 kW and 3,243 kW. If working at an evaporation temperature of 0 oC; 3.133 kW; 3.114 kW; 2,986 kW and 2,804 kW if working at an evaporation temperature of -5 oC; and 2,741 kW; 2,710 kW; 2,611 kW and 2,445 kW if working at an evaporation temperature of -10oC.

Download Full-text

λ-Transition to the Bose-Einstein Condensate

Zeitschrift für Naturforschung A ◽

10.1515/zna-1995-1003 ◽

1995 ◽

Vol 50 (10) ◽

pp. 921-930 ◽

Cited By ~ 8

Author(s):

Siegfried Grossmann ◽

Martin Holthaus

Keyword(s):

Heat Capacity ◽

Three Dimensional ◽

Einstein Condensate ◽

Einstein Condensation ◽

Condensation Temperature ◽

Harmonic Oscillator Potential ◽

Bose Einstein Condensate ◽

Bose Einstein ◽

Analytical Expressions ◽

Grand Canonical

Abstract We study Bose-Einstein condensation of comparatively small numbers of atoms trapped by a three-dimensional harmonic oscillator potential. Under the assumption that grand canonical statistics applies, we derive analytical expressions for the condensation temperature, the ground state occupation, and the specific heat capacity. For a gas of TV atoms the condensation temperature is proportional to N1/3, apart from a downward shift of order N-1/3. A signature of the condensation is a pronounced peak of the heat capacity. For not too small N the heat capacity is nearly discontinuous at the onset of condensation; the magnitude of the jump is about 6.6 N k. Our continuum approximations are derived with the help of the proper density of states which allows us to calculate finite-AT-corrections, and checked against numerical computations.

Download Full-text

Efficiency Evaluation of the Ejector Cooling Cycle using a New Generation of HFO/HCFO Refrigerant as a R134a Replacement

Energies ◽

10.3390/en11082136 ◽

2018 ◽

Vol 11 (8) ◽

pp. 2136 ◽

Cited By ~ 11

Author(s):

Bartosz Gil ◽

Jacek Kasperski

Keyword(s):

High Efficiency ◽

Coefficient Of Performance ◽

Condensation Temperature ◽

Evaporation And Condensation ◽

Wide Range ◽

Theoretical Investigations ◽

Maximum Coefficient ◽

C 30 ◽

New Generation ◽

And Control

Theoretical investigations of the ejector refrigeration system using hydrofluoroolefins (HFOs) and hydrochlorofluoroolefin (HCFO) refrigerants are presented and discussed. A comparative study for eight olefins and R134a as the reference fluid was made on the basis of a one-dimensional model. To facilitate and extend the possibility of comparing our results, three different levels of evaporation and condensation temperature were adopted. The generator temperature for each refrigerant was changed in the range from 60 °C to the critical temperature for a given substance. The performed analysis shown that hydrofluoroolefins obtain a high efficiency of the ejector system at low primary vapor temperatures. For the three analyzed sets of evaporation and condensation temperatures (te and tc equal to 0 °C/25 °C, 6 °C/30 °C, and 9 °C/40 °C) the maximum Coefficient of Performance (COP) was 0.35, 0.365, and 0.22, respectively. The best performance was received for HFO-1243zf and HFO-1234ze(E). However, they do not allow operation in a wide range of generator temperatures, and, therefore, it is necessary to correctly select and control the operating parameters of the ejector.

Download Full-text

Effect of Condensation Temperature on Formaldehyde Release from Durable Press Fabrics

Textile Research Journal ◽

10.1177/004051758805800910 ◽

1988 ◽

Vol 58 (9) ◽

pp. 552-554 ◽

Cited By ~ 2

Author(s):

Drago Katovic ◽

Ivo Soljacic

Keyword(s):

Quantitative Difference ◽

Condensation Temperature ◽

Extraction Temperature ◽

Slow Process ◽

Formaldehyde Release ◽

Durable Press

We investigated formaldehyde release from cotton and polyester/cotton materials treated with DMEU and DMDHEU resins at different condensation temperatures. In the samples treated with DMEU, the amount of free formaldehyde was greater at lower condensation temperatures. Samples treated with DMDHEU gave similar results when the AATCC method for determining formaldehyde was used, but when the MITI method was used, the condensation temperature-formaldehyde curves showed a minimum at about 140°C. The release of formaldehyde is a slow process, because both methods gave similar curves when longer extraction times were used. Changing the extraction temperature gave a quantitative difference.

Download Full-text