• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.349-352
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• 2002

This paper describes a design of a 1bit Carry Propagate Free Adder/Subtracter (CPFA/S) VLSI using the Adiabatic Dynamic CMOS Logic (ADCL) circuit technology. Using a PSPICE simulator, energy dissipation of the ADCL 1bit CPFA/S is compared with that of the CMOS 1bit CPFA/S. As a result, energy dissipation of the proposed ADCL circuits is about 1/23 as low as that of the CMOS circuits. The transistors count, propagation-delay tittle and energy dissipation of the ADCL 4bit CPFA/S are compared with those of the ADCL 4bit Carry Propagate Adder/Subtracter (CPA/S). The transistors count and propagation-delay tittle are found to be reduced by 7.02% and 57.1%, respectively. Also, energy dissipation is found to be reduced by 78.4%. Circuit operation and performance are evaluated using a chain of the ADCL 1bit CPFA/S fabricated in a $1.21mutextrm{m}$ CMOS process. The experimental results show that addition and subtraction are operated with clock frequencies up to about 1㎒.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2358-2367
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• 1992

This paper deals with preliminary design conditions for a thermally actuated Vuilleumier refrigerator/heat pump. The previously reported approximate adiabatic analysis which is based on the 8-volume model makes it possible to evaluate exchanged heats per cycle as well as cyclic pressure, temperature and mass variation of each working volume. Calculated results reveal not only there exists an optimum value for the phase angle and the swept volume ratio maximizing a specific thermal output, but also design parameters can be determined independently of each other. Under a given combination of operating temperature levels, the optimum conditions for refrigeration are different from those for heat pumping and the differences between two operating modes become larger with decreasing the dead volume ratio. Both the optimum phase angle and the optimum swept volume ratio are increased asymptotically toward 0.5 pi and 1.0 respectively, as the dead volume ratio approaches to unity. When a VM machine is used for cooling and heating simultaneously, the design parameters should be carefully determined to reach the best performance.

• Progress in Superconductivity and Cryogenics
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• v.24 no.1
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• pp.23-28
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• 2022

A sorption cooler, which utilizes helium-4 as a working fluid, was previously developed and tested in KAIST. The cooler consists of a sorption pump and a thermosyphon. The developed sorption cooler aims to pre-cool a certain amount of the magnetic refrigerant of an adiabatic demagnetization refrigerator (ADR) from 4.5 K to 2.5 K. To simulate the high heat capacitance of the magnetic refrigerant, liquid helium was utilized not only as a refrigerant for the sorption cooling but also as a thermal capacitor. The previous experiment, however, showed that the lowest temperature of 2.7 K which was slightly higher than the target temperature (2.5 K) was achieved due to the radiation heat leak. This excessive heat leak would not occur when the sorption cooler is completely integrated with the ADR. Thus, based on the experimentally obtained pumping speed, the prediction model for the sorption cooler is developed in this study. The presented model in this paper assumes the sorption cooler is integrated with the ADR and the heat leak is negligible. The model predicts the amount of the liquid helium and the required time for the sorption cooling process. Furthermore, it is confirmed that the performance of the sorption cooler is enhanced by reducing the volume of the thermosiphon. The detailed results and discussions are summarized.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.277-278
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• 2018

Improvement of insulation performance of buildings is a major part. Adiabatic method The adiabatic method minimizes the heat loss of the building. External insulation uses insulation to prevent fire. Ambient air hazards are less prone to fire. When a fire occurs, a phenolic pattern is formed and bond strength with the wall increases. EPS insulation and phenol foam were used to compare external heat transfer and external heat transfer. The heat transfer properties of phenolic foam and styrofoam were evaluated as follows. In the mortar and styrofoam structure, the problem of styrofoam reaching the burning point occurred before the collapse of the mortar, and the phenol foam had a problem in that when the direct fire was continued on the phenol foam. The characteristics of continuous infiltration appeared. In the case of mortar and phenol foam + styrofoam, the heat penetrated into the interior due to the shrinkage due to the shrinkage of the carbon screen on the phenol foam. However, when reinforced with glass mesh on the outer surface, And to reduce infiltration.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.3
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• pp.265-273
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• 2000

Basic simulation program for Vuilleumier cycle heat pump was developed that can use precise VMHP design and analysis. VMHP system was divided 11 sections in simulation. Simulation was used adiabatic model analysis and that considered with heat transfer performance for heat exchanger, regenerator loss, conduction loss, shuttle loss, pumping loss and pressure loss by flow friction. Specially, friction loss of connection pipe between heat compression side and heat pump side, leakage of rod seal and piston seal was considered in the analysis.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.207-210
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• 2002

We had designed thermally controlled superconducting switches using a general nonlinear optimized algorithm with constraints and tested its performance. Objective function was to minimize the total volume of the superconducting switch. And constraints were to have designed resistance in normal status and temperature. In order to compare performance of the optimized superconducting switch, we made another one which had geometrically different parameters but had same structure and resistance value when the superconductor part is normal status by heater. Objective function converged very rapidly. As result, volume of the adiabatic part and total volume of the switch were reduced to more than 70% and 30% respectively. Also, even if same heater power was supplied with NiCr wire heater, the optimized superconducting switch had very fast On-OFF switching performance comparing with unoptimized switch.

• The KSFM Journal of Fluid Machinery
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• v.10 no.3 s.42
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• pp.9-16
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• 2007

Deterioration of surface of turbomachinery blades occurs in course of time due to many factors and hence reduces the performance of the machine. In this paper, the effects of surface roughness of transonic axial compressor blade on performance are studied considering a reference blade and a shape distorted (optimized) blade. Optimal blade is designed considering sweep and lean. Baldwin-Lomax turbulence model is used for flow field analysis and Cebeci-Smith roughness model is formulated for roughness modeling. It is found that, as the surface roughness increases, adiabatic efficiency, total temperature ratio and total pressure ratio decrease while Mach number increases. Performance deterioration is more severe in case of distorted blade as compared to reference blade.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1964-1971
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• 1995

In the present study, the performance characteristics of a centrifugal air compressor were investigated experimentally. The PC controlled performance test facility for a centrifugal air compressor driven by an electric motor with a gear box to achieve higher compressor rotating speed was set up in the present study. The performance test for a turbocharger compressor of a diesel engine was conducted, and in a case of 34,800 rpm, pressure ratio 1.18, flow rate 0.09kg/s, compressor efficiency 61% were investigated. Adiabatic power for a tested compressor showed maximum value at mass flow ratio 0.8. The value of mass flow ratio of maximum efficiency was about 0.37, it was independent of compressor rotating speed.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.72-81
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• 1991

In this study, the analytic investigation of the unsteady flow in the intake and exhaust pipes has been carried out using the method of characteristics in one direction to predict volumetric efficiency. Based on the calculated volumetric efficiency, three zone predictive analysis using Wiebe function was applied to predict the engine performance and the results were compared with experiment. Mixture in the cylinder is subdivided into three zones during combustion process in this analysis; adiabatic core zone, thermal boundary layer zone and unburned zone. In each zone, pressure, temperature and gas composition have been calculated. In conclusion, it is possible to take account of the intake and exhaust pipe tuning effect in predicting the engine performance, by the analytic solution of the unsteady flow in the pipes, and comparison of prediction with experimental results shows a good agreement on the pressure variation in the intake and exhaust pipes which has a direct influence on the volumetric efficiency and performance of the engine.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.6
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• pp.303-309
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• 2013

For air-tight modern buildings, secondary damage is likely to occur due to condensation in the relatively high heat-transmission windows since water vapor is not easy to discharge. Therefore, in this study, condensation performance of vacuum glazing was numerically analysed, compared with that of ordinary glass and confirmed experimentally by three sheets of vacuum glazing manufactured. The results show that the heat transmission coefficient of the vacuum glazing whose internal pressure is $10^{-3}$ torr was as low as about $5.7W/m^2{\cdot}K$. Thus, the condensation performance as well as the adiabatic performance was greatly improved compared to that of the ordinary glass.