With the increasing concerns with the quality and the safety of foods, several standards and guidelines have been developed to improve the design, construction, and operation of storage warehouses. Several cool storage buildings have been constructed in Korea during the last decade. However, there are no specific standards or guidelines for energy use reduction in refrigerated structures. The main objective of this study to determine the impact of various insulation systems on the total cooling load of the cool storage structures with particular consideration given to the product thermal mass effect to find optimal insulation thickness for each envelope component for various climatic locations in Korea. An energy analysis model was developed using the DOE-2.1E program and over 3500 energy simulations were performed. To determine the optimal configuration for die storage building insulation system, life-cycle cost analysis was conducted. The selection of optimal insulation configuration for each climatic location is based on various criteria including those of crop storage owners and of national energy conservation policy. The results presented in this paper provide easy-to-use design guidelines to select optimal insulation thickness for crop storage facility in Korea.

This paper presents an experimental measurement of the thermal conductivity of bovine cortical bone by an improved parallel plate method to increase the accuracy of the measurement. An experimental apparatus was designed to measure the thermal conductivity of the cortical bone using a reference material with a known thermal conductivity by the heat transfer through the samples. To improve the measurement accuracy, a reference material was selected as quartz, which is of the same order of magnitude of the thermal conductivity of bovine cortical bone reported in the existing literature. Additionally, the temperatures at the heat source and heat sink were set to ±5°C from the ambient temperature to reduce the inevitable heat loss in the measurement. The temperature offset was determined numerically. The current experimental measurement was validated by an in-house finite-difference numerical program. The heat loss in the measurement was predicted from the numerical program. The thermal conductivity of the bovine cortical bone was then determined to be 0.55 ± 0.02 W/mK with compensating heat loss.

Liquid transportation without employing a bulky power source, often observed in nature, has been an essential prerequisite for smart applications of microfluidic devices. In this report, a leaf-inspired micropump (LIM) which is composed of thermo-responsive stomata inspired membrane (SIM) and mesophyll-inspired agarose cryogel (MAC) is proposed. The LIM provides a durable flow rate of 30 μl/ḣcm 2 for more than 30 h at room temperature without external mechanical power source. By adapting a thermo-responsive polymer, the LIM can smartly adjust the delivery rate of a therapeutic liquid in response to temperature changes. In addition, as the LIM is compact, portable, and easily integrated into any liquid, it might be utilized as an essential component in advanced hand-held drug delivery devices.

In this paper, boiling experiments were conducted to study two-phase pressure drop and the heat transfer coefficient in a staggered array micro pin fin channel of degassed water at a mass flux range of 9.3 to 46.6 kg/m 2 s and a heat flux of 0.5 to 0.9 W/cm 2 . Copper was used for the pin fin array microchannel heat sink, which was 31 mm in width and 82 mm in length. Micro pin fins, of 400 μm in diameter and 700 μm in height, were manufactured using a micro milling machine on the channel block. The distance between two pin fin surfaces is 300 μm. A thin film heater, which supplies a maximum constant heat flux of 1.55 W/cm 2 , was attached underneath the heat sink. From the experimental results, at a vapor quality of up to 0.04, the boiling heat transfer coefficient decreased as the quality increased. Results show that the heat transfer coefficient is dependent on the mass flux. The data also showed that the pressure drop increased with increasing mass flux. The data obtained in this study were compared to the existing correlations of boiling pressure drop and heat transfer coefficients. Results showed that the correlation with boiling pressure drop of Qu and Siu-Ho [22] yielded a prediction of 21.3% average error Additionally, as a result of comparison with the four existing correlations of boiling heat transfer coefficient, all correlations had a lower prediction for the heat transfer coefficients obtained in this study. Through visualization, it was found that the bubbles generated between the fins began to grow and moved downstream. We observed a stationary vapor pocket in which bubbles did not flow.

There are many attempts to save the cost of transportation. Especially, drag reduction of heavy vehicles such as truck or tractor-trailer have enormous effect on the reduction of fuel consumption and CO 2 emission, because road freight transport using heavy vehicles occupies majority in physical distribution cost.

This paper provides a qualitative evaluation of the impact of advanced fuel cycles, particularly partition and transmutation of actinides, on the uncertainty associated with geologic disposal. Based on the discussion, advanced fuel cycles, will not materially alter (1) the repository performance, (2) the spread in dose results around the mean, (3) the modeling effort to include significant features, events, and processes in the performance assessment, or (4) the characterization of uncertainty associated with a geologic disposal system in the regulatory environment of the United States.

Precisely evaluation of the reliability of aging structure is essential, particularly in the oil gas industry where inaccurate predictions of structural performance may have significant hazardous consequences. Related to this issue, it is important to predict the corrosion behavior of the gas pipeline structure used in the production of gas in subsea area. As corrosion is concerned, the effects of pipeline failure due to significant reduction of burst strength will make it hard for the pipeline operator to maintain the serviceability of pipelines. Therefore related to this problem, the resistance service of the pipeline is assessed by means of burst strength capacity. In this study, the critical part of the corrosion along 2.4 km pipeline is assessed using two approaches; empirical design codes formula and ANSYS numerical analysis. The future integrity of the pipeline is then assessed to predict the remaining year in service for the aging pipeline. The results and outcomes of the present study will be useful for evaluating the pipeline integrity as well as the prediction of the remaining life of in service aging pipeline structures.

Recently vertical or horizontal type condensation heat exchangers are being studied for the application to secondary passive cooling system of nuclear plants. To design vertical condensation heat exchanger in water pool, a thermal sizing program of condensation heat exchanger, TSCON (Thermal Sizing of CONdenser) was developed in KAERI (Korea Atomic Energy Research Institute). In this study, condensation heat transfer correlation of TSCON is evaluated with the existing experimental data set to design condensation heat exchanger without non-condensable gas (pure steam condensation). From the investigation of the existing condensation heat transfer correlation to the existing experimental data, the improved Shah correlation showed most satisfactory results for the heat transfer coefficient and mass flow rate in a heat exchanger in both subcooled and saturated water pools without the presence of non-condensable gas.

Quantitative computed tomography (QCT) scans have been used to estimate bone mineral density (BMD) measurements, which in turn have been shown to correlate with bone mechanical properties such as strength, stiffness and yield load 1,2 . Information on the variation of BMD in the cervical spine with respect to anatomic location and vertebral level does not currently exist. This would be beneficial to vertebral instrumentation designers and to basic scientists who assign mechanical properties of bones in finite element models of the spine. Previously, bone mineral density measurements of the cervical spine have been performed almost exclusively on the central vertebral body, either by measuring trabecular BMD in a single CT slice 1, 3, 4 or by measuring a large volume of trabecular bone in multiple CT scan slices 5,6 . In addition to the central vertebral body, the only other BMD measurements of specific anatomical regions were performed on the endplates 2, 3 .

NASA has been studying future transport concepts, envisioned to be technically realizable in the timeframe of 2020–2030, to meet environmental and performance goals. One concept receiving considerable interest involves a propulsion system embedded into a hybrid wingbody aircraft. While offering significant advantages in fuel savings and noise reduction by this concept, there are several technical challenges that are not encountered in the current fleet and must be overcome so as to deliver target performance and operability. One of these challenges is associated with an inlet system that ingests a significantly thick boundary layer, developing along the wingbody surface, into a serpentine diffuser before the flow meeting fan blades. The flow is subject to considerable total pressure loss and distorted at the fan face, much more significantly than in the inlet system of conventional aircraft. In our previous studies [1, 2], we have shown that through innovative design changes on the airframe surface, it is possible to simultaneously increase total pressure recovery and decrease distortion in the flow, without resorting to conventional penalty-ridden flow control concepts, such as vortex generator or boundary layer bleeding/suction. In the current study, we are interested in understanding the following issues: how the embedded propulsion system performs under a crosswind condition by studying in detail the flow characteristics of two inlets, the baseline and another optimized previously under the cruise condition. With the insight, it is hoped that it can help in the follow-on study by devising effective strategies to minimize flow distortion arising from the integration of an embedded-engine system into an airframe to the level acceptable to the operation of engine fan.

Synchrotron X-ray computed tomography was employed to measure the volume variation of gas diffusion layer (GDL) for polymer electrolyte fuel cell (PEFC). The study was conducted using 3D reconstruction (or a 3D rendering software) of orthoslice images. Especially, the temporal variation of structural parameters such as porosity was measured under freeze and thaw cycles. The freezing and thawing cycle were generated using a CRYO-system and an external light source alternatively. As a result, the structural parameters such varied significantly between the successive freeze/thaw cycles and irreversible change was also observed.

A numerical study of subcooled onset of nucleate boiling (ONB) in a micro-channel under pulsed heating using the volume of fluids (VOF) model was conducted. The ONB time was determined when the void fraction at the microheater surface starts to exist. A smooth thin Pt heater was located between the water in the channel and the solid material. The theoretical superheat for homogeneous nucleation did not predict the transient ONB results of convective flow of water. Once heat load increases at the heater, transient flow boiling starts to occur. From a parametric study, it was found that the time constant increases with large substrate thermal diffusivity, low Reynolds number, and large channel diameter.

A network analysis was established to model the array of evaporative micro-channels with possible non-uniformity heating as well as branching of the channels. Iterative solution of the evaporative micro-channel network can be obtained using the Hardy-Cross method together with accurate two-phase head-loss correlations. Based on the experimental evidence, cross-cutting micro-channels reduce the uneven flow distribution in parallel micro-channels at non-uniform heating. Through this network analysis, it is also evident that cross-cutting grooves on parallel micro-channels are effective in reducing non-uniform heating effects and enhancing the uniform wall temperature distribution.

This study seeks to analyze and explore experimental methods to study condensation heat transfer in micro- and mini-channel. Following, an experimental setup was built and initial results are presented. Several experimental techniques were reviewed, while two, thermoelectric coolers and a copper-heat-flux-sensor were analyzed in detail for condensation heat flux. It was concluded that thermoelectric coolers were not suitable as heat flux sensors for single-phase validation, but the copper-heat-flux-sensor was appropriate to measure heat transfer coefficients at the mini-scale. Condensation heat transfer coefficients were obtained experimentally in seven parallel square mini-channels of diameter 1mm. Existing condensation correlations were applied to these data; micro- and mini-scale correlations captured the appropriate trends, but the macro-scale Shah (1979) correlation fit the data best.

A study of boundary-layer-ingesting flow in an upper-mounted offset inlet in NASA’s hybrid wing body transport concept for achieving environmental and performance requirements has been carried out. The study aims specifically at minimizing flow distortion stemming from the ingested low-momentum fluid to the level acceptable to the operation of fan blades. In this paper, we will focus on using a discrete adjoint method to arrive at an optimized wall geometry, which is parametrically represented by design variables, for transonic turbulent flows described by 3D Navier-Stokes equations supplemented with κ–ω–SST turbulence model. Of special interest herein is the flow physics resulting from optimization, revealing the intricate connections to the remarkable reduction in flow distortion and total pressure losses at the engine face. It is discovered that the secondary counter-rotating vortex pair commonly seen in an S-inlet is eliminated by energizing both core and boundary-layer fluids through the change of wall shape by a series of peaks and valleys, whose magnitudes and wave forms being functions of locations and unknown a priori are determined by the discrete adjoint method. Moreover, the optimal shape still holds similar level of superior performance at off-design conditions. The result may suggest a possible paradigm shift in flow control concept, away from disruptive penalty-ridden devices, by properly conditioning and guiding the flow.

Recently microscale flows have been receiving large attention in various research areas. However, most conventional imaging techniques are unsatisfactory due to difficulties encountered in the visualization of microscale flows. Recent advances in optics and digital image processing techniques have made it possible to develop several advanced micro-PIV/PTV techniques. They can be used to obtain quantitative velocity field information of various microscale flows from visualized images of tracer particles. As new advanced micro-PIV techniques, the basic principle and typical application of the time-resolved micro-PIV and X-ray micro-PTV methods are explained. As 3D velocity field measurement technique that can be used to measure microscale flows, the holographic micro-PTV method is introduced. These advanced PIV/PTV techniques can be used to reveal the basic physics of various microscale flows and will play an important role in visualizing hidden microscale flow phenomena, for which conventional methods have many difficulties to analyze.

It is now widely recognized that three-dimensional (3D) system integration is a key enabling technology to achieve the processing speeds and performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D stacked ICs, interlayer microfluidic cooling scheme is adopted and analyzed in this study. The effects of cooling scheme and essential geometry variations on the routing completion and congestion of electrical interconnect are quantitatively analyzed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that refrigerants in two-phase flow are thermally preferred due to the higher heat transfer coefficients, and relatively constant fluid temperature throughout the microchannel. However, the large internal pressure and pressure drop act as significant limiting factors in realizing the merits of two-phase cooling. It is also concluded that integration of high performance hot-spot thermal management is a key to addressing a challenge of mass flow rate mal-distribution.

Water management in a polymer electrolyte fuel cell (PEFC) was experimentally investigated using an X-ray microscopy technique. Recently, fuel cell has been receiving large attention as an important renewable energy due to its efficiency, clearness and sustainability. Among various types of fuel cells, PEFC can be used as a power source of transport vehicles and home applications. In recent commercial development of PEFC, water management is one of the major problems to be solved. In fact, proper water management is vital to enhance performance and durability of PEFC. In this study, transport of water inside MEA (membrane electrode assembly) and GDL (gas diffusion layer) layers of an operating ( in situ ) fuel cell was observed using the synchrotron X-ray micro-imaging technique. As the synchrotron X-ray imaging technique has very high spatial and temporal resolutions, it is suitable for observing the dynamic movement and behavior of liquid layer and water distribution inside the PEFC. For this X-ray micro-imaging experiment, a single cell test kit of PEFC was specially designed for convenient capturing of X-ray images. Temporal variation of gray level in the PEFC components, such as MEA, GDL and endplate, was investigated with varying loading condition. As a result, X-ray images of the PEFC components were clearly distinguished by image pattern and gray level difference. The gray level shows roughly symmetric distribution with respect to MEA layer. The gray level at GDL decreases with lapse of time, indicating the increase of H 2 O concentration with time.