• 설비공학논문집
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• 제10권2호
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• pp.202-216
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• 1998

A computer simulation for the performance analysis of automobile air conditioning components is carried out for the various operating conditions. The automobile air conditioning system consists of laminated type evaporator, swash plate type compressor, parallel flow type condenser, externally equalized thermostatic expansion valve and receiver drier. The overall heat transfer coefficient and the pressure drop in laminated type evaporator were obtained through experiments. In parallel flow type condenser, the performance analysis computer program using the empirical equation for heat transfer coefficient has been developed and the results are compared with experimental results. A model for matching the performance analysis programs of respective components .of automobile air conditioning system is introduced. Further, the effects of varying condenser size and refrigerant charge on the performance of automobile air conditioning system are discussed clearly.

• 대한기계학회논문집B
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• 제33권3호
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• pp.170-177
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• 2009

In the present study, a finite element analysis of conjugate heat transfer problem inside a cavity with a heat-generating conducting body, where constant heat flux is generated, is conducted. A conduction heat transfer problem inside the solid body is automatically coupled with natural convection inside the cavity by using a finite element formulation. A finite element formulation based on SIMPLE type algorithm is adopted for the solution of the incompressible Navier-Stokes equations coupled with energy equation. The proposed algorithm is verified by solving the benchmark problem of conjugate heat transfer inside a cavity having a centered body. Then a conjugate natural heat transfer problem inside a cavity having a heat-generating conducting body with constant heat flux is solved and the effect of the Rayleigh number on the heat transfer characteristics inside a cavity is investigated.

• Journal of applied mathematics & informatics
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• 제35권5_6호
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• pp.439-447
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• 2017

This paper investigates the inverse problem of determining an unknown heat radiative coefficient, which is only time-dependent. This is an ill-posed problem, that is, small errors in data may cause huge deviations in determining solution. In this paper, the existence and uniqueness of the problem is established by the second Volterra integral equation theory, and the method of trace-type functional formulation combined with finite difference scheme is studied. One typical numerical example using the proposed method is illustrated and discussed.

• Journal of Advanced Marine Engineering and Technology
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• 제19권4호
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• pp.27-33
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• 1995

The turbulent flow and heat transfer in the tunnel laminar flow type clean room is investigated by a numerical simulation. The model clean room is assumed to be a rectngular $5m\times3m$, in which a worktable of 0.75m hight, and 1.5m or 3m long at the floor. Major parameters are the inlet flow velocity, inlet hole size and worktable surface distance. The mean Nusselt number is increased by increasing Reynolds number and can be expressed by the correlation equation.

• 한국추진공학회지
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• 제16권2호
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• pp.42-50
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• 2012

열전달 연구의 목적은 온도와 열유속 분포를 보다 정확하게 예측하는 것이다. 이를 위해 상용 CFD 코드인 FLUENT를 사용하여 2종류의 노즐에 대해 질량유속비와 압력비를 계산하였으며, 실험결과와 잘 일치하였다. 또한 1종류의 노즐에 대해 FLUENT를 사용한 노즐 벽면에서의 열전달계수 계산결과는 노즐 축소부에서 실험결과 보다 약간 크게 예측되었으나 확대부에서는 잘 일치하고 있다. Bartz식을 이용한 열전달계수 계산결과는 전체적으로 실험결과 보다 크게 예측되었다. 계산결과가 실험결과와 차이를 보이는 원인은 노즐 내 급가속 유동에 의한 층류화, 난류모델 및 격자구성 등을 고려해 볼 수 있다.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.18-24
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• 2015

In this study, a $CO_2$ air-conditioning system was investigated with different types of electrically driven compressors, parallel flow type gas cooler, four-pass type evaporator, internal heat exchanger integrated with accumulator, and electric expansion valve. The experimental study was conducted under various operating conditions (ie., different rotational compressor speeds, air inlet temperatures and air velocity coming into heat exchangers). The experimental results showed the cooling capacity was 3.5kW at $35^{\circ}C$ ambient temperature when the vehicle was idle (ie., the worst condition for cooling off the gas cooler). In terms of performance effect of the compressor, the e-RP model had a slightly better cooling capacity and coefficient of performance than the e-GR model under the same test conditions. An experimental equation for optimum cooling-performance control was also suggested based on the results. A high-pressure control algorithm for the super critical cycle was determined to achieve both maximum cooling performance and efficient energy consumption. The results from the experimental equation coincided with those of previous experimental studies.

• 대한기계학회논문집B
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• 제21권11호
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• pp.1466-1474
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• 1997

In order to design and develop a spark ignition engine, many studies must be preceded about the characteristics of thermal flow. For measurement of transient wall temperature thin film thermocouples of Bendersky type were manufactured and these probes were fixed into the wall of combustion chamber. Surface wall temperatures were measured in experiments of various engine speeds. Transient heat fluxes were calculated from the wall temperature measurements. Pressure was measured from combustion chamber using pressure transducer and gas temperatures were calculated using the state equation of ideal gas. And instantaneous heat transfer coefficients were obtained. It will be the basic data for the formulae of instantaneous heat transfer coefficients.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제18권3호
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• pp.231-244
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• 2011

We prove the Hyers-Ulam stability for trigonometric type functional inequalities in restricted domains with time variables. As consequences of the result we obtain asymptotic behaviors of the inequalities and stability of related functional inequalities in almost everywhere sense.

• 충청수학회지
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• 제21권3호
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• pp.361-370
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• 2008

We consider the Hyers-Ulam type stability of the Cauchy, Jensen, Pexider, Pexider-Jensen differences: $$(0.1){\hspace{55}}C(u):=u{\circ}A-u{\circ}P_1-u{\circ}P_2,\\(0.2){\hspace{55}}J(u):=2u{\circ}\frac{A}{2}-u{\circ}P_1-u{\circ}P_2,\\(0.3){\hspace{18}}P(u,v,w):=u{\circ}A-v{\circ}P_1-w{\circ}P_2,\\(0.4)\;JP(u,v,w):=2u{\circ}\frac{A}{2}-v{\circ}P_1-w{\circ}P_2$$, with respect to bounded distributions.

• Journal of Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.779-784
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• 2005

This paper presents the theory of similarity transformations applied to the momentum and energy equations for laminar, forced, external boundary layer flow over a horizontal flat plate which leads to a set of non-linear, ordinary differential equations of phase change material slurry(PCM Slurry). The momentum and energy equation set numerically to obtain the non-dimensional velocity and temperature profiles in a laminar boundary layer are solved. The heat transfer characteristics of PCM slurry was numerically investigated with similar method. It is clarified that the similar solution method of Newtonian fluid can be used reasonably this type of PCM slurry which has low concentration. The data of local wall heat flux and convective heat transfer coefficient of PCM slurry are higher than those of water more than 150$\~$200$\%$, approximately.