• Solar Energy
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• v.20 no.2
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• pp.9-17
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• 2000

To obtain thermal performance data, an experiment was performed with the two selected thermosyphon systems. The system parameters obtained by experimental data were used to perform TRNSYS simulation and verified TRNSYS model of thermosyphon solar hot water system. The thermosyphon solar hot water system was TYPE 145 which is modified from non-linear model. This model can describe heat exchange type and non-linear efficiency equation. It is possible to analyze the annual energy rate with efficiency equation and system specification. In this paper, we could compare the annual performance of the coil heat exchanger with that of the tank-in-tank heat exchanger. Under the same efficiency and parameter, heat exchange, drain, initial tank temperature, ratio of tank volume over collector area(V/Ac), regional annual performance rating were performed.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.263-270
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• 2008

The capillary tube/suction line heat exchanger (SLHX) is widely used in small refrigeration systems. The refrigerant flowing in the SLHX experiences frictional and accelerational head losses, flashing, and heat transfer simultaneously. The simulation of refrigerant flow through SLHX is important since this will help engineers analyze and optimize the SLHX incorporated in a refrigeration system. The present SLHX model is based on conservation equations of mass, momentum and energy. Also a meta-stable model is included. All these equations are solved simultaneously. In this paper, HFC-134a refrigerant flow through a non-adiabatic capillary tube is simulated. The simulation results are discussed but not validated against experimental measurements yet.

• Nuclear Engineering and Technology
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• v.39 no.2
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• pp.95-102
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• 2007

The conceptual design of the MIT modular pebble bed reactor is described. This reactor plant is a 250 Mwth, 120 Mwe indirect cycle plant that is designed to be deployed in the near term using demonstrated helium system components. The primary system is a conventional pebble bed reactor with a dynamic central column with an outlet temperature of 900 C providing helium to an intermediate helium to helium heat exchanger (IHX). The outlet of the IHX is input to a three shaft horizontal Brayton Cycle power conversion system. The design constraint used in sizing the plant is based on a factory modularity principle which allows the plant to be assembled 'Lego' style instead of constructed piece by piece. This principle employs space frames which contain the power conversion system that permits the Lego-like modules to be shipped by truck or train to sites. This paper also describes the research that has been conducted at MIT since 1998 on fuel modeling, silver leakage from coated fuel particles, dynamic simulation, MCNP reactor physics modeling and air ingress analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1630-1633
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• 2003

Hair pin bending machine is pipe forming machine consisting of heat exchanger product system. Hair pin produced by these machine is pathway of refrigerant and play a important role improving the performance and productivity of heat exchanger. The core technology of hair pin bending machine is forming the straight pipe into U-type without any defaults. Therefore, this paper study the relation between the pipe bending forming and the shape and position of mandrel using the elastic-plastic finite element analysis and provide a foundation technology for which developing the hair pin bending machine. The results are followed 1. Mandrel located in front of rotating center of bending die minimized the circular shape variation of copper pipe. 2. Diameter change of mandrel hardly effect the pipe shape.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.701-705
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• 2009

After revision of law of architecture in 2006, all houses which have more 100 households must has ventilation unit for the indoor air quality. Optimal design of the natural and the mechanical ventilation has being considered. In this paper, it is carried out about optimal design for airflow distribution of total heat exchanger in houses using CFD. As the result, first design of ventilation has some problem in porch area. Adding diffusers in porch area and changing diffuser schedule make more efficient ventilation than original design.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.761-768
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• 2008

This paper presents the results of a laboratory study on the thermal conductivity of sand(silica, quartzite, limestone, sandstone, granite and masonry sand)-water mixtures used in ground heat exchanger backfilling materials. Nearly 260 tests were performed in a thermal conductivity measuring system to characterize the relationships between the thermal conductivity of mixtures and the water content. The experimental results show that the thermal conductivity of mixtures increases with increasing dry density and with increasing water content. The most widely used empirical prediction models for thermal conductivity of soils were found inappropriate to estimate the thermal conductivity of unsaturated sand-water mixtures. An improved model using a exponential relationship to compute the thermal conductivity of dry sands and empirical relationship to assess the normalized thermal conductivity of unsaturated sand-water mixtures is presented.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.260-269
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• 2020

The Steam Assisted Gravity Drainage (SAGD) process is an enhanced method to extract oil from bitumen which involves surface and central process facilities. This paper describes the Central Process Facilities (CPF) of SAGD and proposes several retrofit plans to the Heat Exchanger Network (HEN). In this approach, the process integration scheme is applied to estimate the energy saving in HENs, and various cases are modeled in favor of a commercial simulator. Throughout this work, a minimum approach temperature of 10℃ is assumed. The results reveal that, due to the HEN optimization using process integration, the heating and cooling duties can be reduced to 29.68MW and 1.886MW, respectively. Compared with the Husky case, all cases considered in this study indicate a potential reduction of at least 6% in total cost, including investment and operation costs.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.165-168
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• 2011

In this paper, the hybrid tube expander unit for fin and tube type heat exchanger are developed by means of enlarging and inserting the smooth tube with a small diameter to a finned tube having larger diameter. In other word, the tube expander tool that is easy to attach and remove from tube is developed. The hybrid tube expander unit developed in this study can move easily and enlarge the tube without fixing at tube sheet. Also, this unit has a function removing scales inside tube by replacing a tube expander ball.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.5
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• pp.342-350
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• 2008

This paper presents the results of a laboratory study on the thermal conductivity of sand (silica, quartzite, limestone and masonry sand)-water mixtures used in ground heat exchanger backfilling materials. Nearly 150 tests were performed in a thermal conductivity measuring system (TPSYS02) to characterize the relationships between the thermal conductivity of mixtures and the water content. The results show that the thermal conductivity of mixtures increases with increasing dry density and with increasing water content. The results also show that for constant water contents and a dry density value, the thermal conductivity of mixtures increases with increasing thermal conductivity of solid particles. The measurement results were also compared with the most widely used empirical prediction models for the thermal conductivity of soils.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.713-718
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• 2006

This paper concerns the measurement of thermal conductivity of grouting materials for ground loop heat exchanger. A thermal conductivity meter, QTM-500 based on modified transient hot wire method was used to measure the thermal conductivity of neat bentonite and mixtures of bentonite and various additives. Relative to the total mixture mass, as the percent additive was increased the mixture thermal conductivity increased. For the bentonite-silica sand mixtures, the higher density of the sand particles resulted in much higher mixture thermal conductivity.