Ventilation system can have significant influences on the energy consumption, especially in factories with high thermal loads. To remove generated thermal and mass loads from manufacturing areas, several mechanisms can be applied: mixing and layering ventilation. This paper shows experimental studies to compare mixed and stratified ventilation systems for industrial buildings. These experiments were conducted in a factory model with a scale of 1:2.5. The measurements consist of vertical distribution of carbon dioxide concentration and temperature in the ambient room. Additionally, a simulation study was conducted based on the same factory model to predict the annual energy demand of mixed and stratified ventilation systems in different climatic regions. The simulation models were validated with measurements from machines and devices in the authors’ laboratories and in the factories of project partners. The results show advantages in airflow, air quality, cooling capacity and energy demand at different climatic zones when using stratified ventilation.

This paper presents energy performance of hybrid ground source heat pump system used in a hotel building under a hot and humid climate condition. The performance data of a heat pump used in the building have been measured for several weeks. Based on the measured performance data of the heat pump, the building using a hybrid ground source heat pump system is first simulated using an energy simulation program. The building simulation model is then calibrated using monthly utility data. Finally, the calibrated building model using a hybrid ground source heat pump system is used to determine an economical effect of climatic and other factors to this building. The results are compared to those of the building using a conventional air source heat pump system and are used to find the advantage and disadvantage of a hybrid ground source heat pump system against a conventional system under a hot and humid climate condition.

One of the major concerns affecting the safety of bridges with foundation supports in river-beds is the scouring of river-bed material from bridge supports during floods. Scour is the engineering term for the erosion caused by water around bridge elements such as piers, monopiles, or abutments. Scour holes around a monopile can jeopardize the stability of the whole structure and will require deeper piling or local armoring of the river-bed. About 500,000 bridges in the National Bridge Registry are over waterways. Many of these are considered as vulnerable to scour, about five percent are classified as scour critical, and over the last 30 years bridge failures caused by foundation scour have averaged about one every two weeks. Therefore it is of great importance to predict the correct scour development for a given bridge and flood conditions. Apart from saving time and money, integrity of bridges are important in ensuring public safety. Recent advances in computing boundary motion in combination with mesh morphing to maintain mesh quality in computational fluid dynamic analysis can be applied to predict the scour hole development, analyze the local scour phenomenon, and predict the scour hole shape and size around a pier. The main objective of the present study was to develop and implement a three dimensional iterative procedure to predict the scour hole formation around a cylindrical pier using the mesh morphing capabilities in the STARCCM+ commercial CFD code. A computational methodology has been developed using Python and Java Macros and implemented using a Bash script on a LINUX high performance computer cluster. An implicit unsteady approach was used to obtain the bed shear stresses. The mesh was iteratively deformed towards the equilibrium scour position based on the excess shear stress above the critical shear stress (supercritical shear stress). The model solves the flow field using Reynolds Averaged Navier-Stokes (RANS) equations, and the standard k–ε turbulence model. The iterative process involves stretching (morphing) a meshed domain after every time step, away from the bottom where scouring flow parameters are supercritical, and remeshing the relevant computational domain after a certain number of time steps when the morphed mesh compromises the stability of further simulation. The simulation model was validated by comparing results with limited experimental data available in the literature.

Cryosurgery is also called as cryoablation or cryoleision. The third generation of cryo-machine use argon gas for cooling and helium for rewarming to destroy cancer cells. The probes may be put into the tumor during surgery or through the skin (percutaneously). After cryosurgery, the frozen tissue thaws and is either naturally absorbed by the body (for internal tumors), or it dissolves and forms a scab (for external tumors). The main purpose of this paper is to establish a preliminary computer assisted simulation in prostate tumor cryosurgery. A radiologist and an urologist in a medical center in addition to the engineering specialist from the university participated in this interdisciplinary research program. The first step of this simulation protocol is to trim hundreds of two-dimensional medical imaging photos from a patient through the imaging reconstructive software into building a three-dimensional solid modeling. The image data for each patient can be obtained from the x-ray computed tomography (CT), or magnetic resonance imaging (MRI) in the imaging department of hospital. It has successfully built up the related knowledge to overcome the complicacy between the medical imaging modalities and engineering graphic solid modeling with high resolution. It is worthy to mention here that the present solid modeling of prostate can demonstrate the variable diameters and courses of the prostate urethra in vivo. The second step focuses on thermal calculation. So far, there has been no existing commercial software for the specific purpose of the bioheat transfer problem. Hence, user subroutines must be added to the existing commercial software to simulate the clinical situation of cryosurgery. For example, the occurrence of phase change during some specified temperature range and the latent heat of fusion are also incorporated into bio-heat transfer model. It has successfully incorporated bioheat transfer model into the software program to fit the reality in thermal medicine. The third step supplies the data and knowledge concerned with the position of a tumor and the related mechanism of metabolism of living tissue and vessels. The number of probes, the position of each probe, and the operating time of each probe will be explored to ensure a complete killing of the tumor tissue while saving as much healthy surrounding tissue as possible. In this study, the three-dimensional transient temperature distributions based on cryosurgery for prostate tumors have been performed for several cases to find the optimal operating conditions. Different cryoprobes with different freezing time are considered to find the temperature distribution. The simulation results for cryosurgery of prostate tumors will be supplied for practicing physicians as reference to greatly improve the effectiveness of cryosurgery.

This work attempts to develop a physical simulation model for the purpose of studying the effect of various design parameters on the performance of a packaged liquid chiller. A computer model which simulates the steady-state cyclic performance of a vapor compression chiller is developed for the purpose of performing detailed physical design analysis of actual industrial chillers. The model can be used for optimizing design and for detailed energy efficiency analysis of packaged liquid chillers. The simulation model takes into account presence of all chiller components such as compressor, shell-and-tube condenser and evaporator heat exchangers, thermostatic expansion valve and connection pipes and tubing’s by thermal-hydraulic modeling of heat transfer, fluids flow and thermodynamics processes in the chiller’s components. To verify the validity of the developed model, a 7.5 USRT packaged-liquid chiller is used and a laboratory test stand for brining the chiller to its standard steady-state performance condition is build. Experimental results obtained from testing the chiller in different load and temperature conditions are shown to be in good agreement with those obtained from simulating the performance of the chiller using the developed computer model. To optimize the chiller design, an entropy-minimization-optimization analysis is performed based on the analytical performance model of the chiller. The variation of design parameters in construction of shell-and-tube condenser and evaporator heat exchangers are studied using the developed performance and optimization analysis and simulation model and a best-match condition between the physical design and construction of chiller heat exchangers and its compressor is found to exist. It is expected that manufacturers of chillers and research organizations interested in developing energy-efficient design and analysis of chillers can take advantage of the presented study and its results.

Thermal characteristics of an EO (Ethylene Oxide) reactor are analyzed to investigate its structural integrity against thermal loads. A two-dimensional axisymmetric simulation model of the whole reactor structure is developed. A porous media model for the long tube bundle packed with catalyst and a flow resistance model for the thin impingement baffle is proposed to simplify the reactor. Simultaneous simulation of fluid and solid zone for a part with many holes is applied to analyze heat transfer of tubesheet which is connected with the tube bundle and the outer shell. The EOC (End of Catalyst Cycle) condition is used for the normal operation condition because general temperature of the EOC condition is the highest during operation cycle. Transient heat transfer analysis is also conducted to simulate the abnormal ignition in the reactor. Two kinds of ignitions are investigated and thermal diffusion in the reactor during the expected shutting down time is simulated as well. Three-dimensional local heat transfer analysis based on the two-dimensional whole analysis is conducted for the local stress evaluation of the product nozzle elbow and the impingement baffle. Results of the heat transfer analysis have been utilized as a thermal boundary condition for the further structural analysis.

The purpose of this work is to develop a physical simulation model for the purpose of studying the effect of various design parameters on the performance of a packaged liquid chiller. A computer model which simulates the steady-state cyclic performance of a vapor compression chiller is developed for the purpose of performing detailed physical design analysis of actual industrial chillers. The model can be used for optimizing design and for detailed energy efficiency analysis of packaged liquid chillers. The simulation model takes into account presence of all chiller components such as compressor, shell-and-tube condenser and evaporator heat exchangers, thermostatic expansion valve and connection pipes and tubing’s by thermo-hydraulic modeling of heat transfer, fluids flow and thermodynamics processes in each one of the mentioned components. To verify the validity of the developed model, a 7.5 USRT packaged-liquid chiller is used and a laboratory test stand for brining the chiller to its standard steady-state performance condition is build. Experimental results obtained from testing the chiller in various load and temperature conditions are shown to be in good agreement with those obtained from simulating the performance of the chiller using the computer prediction model. In part II of this work, an entropy-minimization-optimization analysis is performed based on the developed analytical performance model of the chiller. The variation of design parameters in construction of shell-and-tube condenser and evaporator heat exchangers are studied using the developed performance and optimization analysis and simulation model and a best-match condition between the physical design and construction of chiller heat exchangers and its compressor is found to exist. It is expected that manufacturers of chillers and research organizations interested in developing energy-efficient design and analysis of chillers can take advantage of the presented study and its results.

Two dimensional simulation models for a solid oxide fuel cell (SOFC) including gas channels have been studied using the commercial software FEMLAB which has a multi-physics approach. The models include full coupling between the mass balances at the anode and cathode, the balance of the ionic current carried by the oxide ion, and a balance of electronic current with an assumption of isothermal conditions. Three cross-section areas of 1cm × 1cm, 3cm × 3cm, and 5 cm × 5cm were chosen to study the dimensional effect. An additional 1cm × 1cm channel with rectangular protrusions was also studied to investigate geometry effects. Simulation results show expected result of increases in fuel cell properties like convective flux, electric potential with increasing cell flow area. The smaller fuel cell surface is altered by adding rectangular protrusions to increase surface area. The presence of rectangular protrusions also show increased current density production compared to a wall without protrusions. It is expected that the proposed simulations can be used to significantly help the design and operation of a SOFC in practical applications.

It is well known that drilling is one of the most difficult metalwork cutting operations, not only from the viewpoint of manufacturing process, but also from the thermal management point of view of the drill. For the drilling process, due to its long time continuous metal-to-metal friction between drill tip edge and work piece, a significant amount of heat is generated on the interface, which is in a confined space compared to other machining processes, such as cutting or milling. This makes it very difficult to keep the temperature of drill tip under a certain but acceptable range since the coolant is unable to penetrate deep enough into the hole. Also, based on the environmental considerations and the cost reduction requirement, the conventional flooding coolant method become highly inefficient and expensive due to high maintenance costs. A new approach, dry drilling method (i.e., no coolant is employed during the drilling process) is investigated in this study. In dry drilling, we used heat pipe technology to accomplish the goal of efficient heat removal from the drill tip. It is heat pipe’s unique and excellent advantages such as, high reliability, supreme equivalent thermal conductivity, flexible adaptability and so forth, that make it possible for dry drilling by combining the drill and heat pipe. From the numerical simulation viewpoint of heat pipe drill, how to correctly model the heat pipe in the drill is one of the crucial tasks because it will directly influence the accuracy of the simulation results. So far, there are few different kinds of simulation models for heat pipe drill and each of them works well in some kinds of special situations. The present paper studied and compared these different simulation models of heat pipe and then proposed a general, simple but robust and more accurate approach to simulate the heat transfer process in the heat pipe drill. Furthermore, this kind of the heat pipe model can be used in many other heat pipe applications.

Air-cooled condenser used for refrigeration and heat pump applications generally consists of plate-fin-tubes. A universal simulation model has been developed for simulation of plate-fin-tube condenser with distributed-parameter method. The model discretizes coil into circuit to circuit, tube to tube and then node to node along the refrigerant path and carries out repetitive marches from the refrigerant inlet to its outlet while simultaneously updating the values of the air stream properties for obtaining quick convergence. Unlike previous models, this model is capable of analyzing complicated circuiting arrangements and can take into count the variation in heat transfer coefficient and pressure drop coefficient along the tube. Especially, the coefficient of heat transfer and pressure drop of two-phase refrigerant strongly influences each other, so the pressure balance among parallel refrigerant circuits is carried out by adjusting the mass flow rate of refrigerant in each circuit. The distinguishing feature of this model is that it performs a node-to-node discretized analysis of the condenser along each circuit, making fewer assumption about the nature of heat transfer and pressure drop than traditional models. The model has been validated against experimental data on such coils available in the literature. It is not only helpful for optimal design of air-cooled condenser with any kind of complex circuiting arrangement, but also can act as a main part of the simulation model of refrigeration and heat pump systems.