At Saint Martin’s University, the Mechanical Engineering Department incorporates design throughout the curriculum, starting from the freshman course ‘Introduction to Engineering’ up through the senior capstone design. Undergraduate Mechanical Engineering students are required to take three Mechanical Engineering elective courses. Each of these elective courses is 3 credits; one of these credits must be design. For ME 436 Thermal Design of Heat Exchangers course, the students were assigned a project to meet the Accrediting Board of Engineering and Technology student outcome criteria a, b, c, d, e, g, and i. In addition to course work the students designed, market searched for parts, budgeted, manufactured and built, then tested a finned helical coil heat exchanger experiment. A limited budget was assigned for this project. Currently, the apparatus is being used as an additional experiment in the Thermal Engineering Laboratory. This article includes the preliminary design, final design, experimental results, and assessment by students and faculty.
The paper industry is the second largest consumer of energy in the Northwest. The majority of energy consumption in any paper mill occurs in the paper dryer section. This article presents a unique, complete dryer section design that is more economical than conventional paper dryers. The proposed dryers use infrared radiation as the primary form of heat transfer. The infrared dryer section design is compared to the conventional steam dryer section for a high speed newsprint paper machine. Since conventional steam dryer sections in paper machines are a major capital investment and last for decades, a simple, economical retrofit design of a conventional dryer section is included.
An enormous number of empirical and analytical closed solution, single phase, internal flow heat transfer correlations exist in the open literature. This article is a compilation of single phase internal convective heat transfer correlations in straight, circular conduits. These correlations cover convective internal flow of various Newtonian fluids under a wide range of heating conditions, and orientations for the different flow regimes. In the past some engineers extended the use of some correlations beyond their limits. The purpose of this article is to compile internal flow heat transfer correlations in one source, to alleviate time required by the practicing engineer to research the literature for correlations to meet specific conditions.
Traditionally, heat pumps and refrigerators utilize the vapor compression cycle to achieve cooling. These vapor compression cycles use hydrochlorofluorocarbons (R134a) as the cycle’s working fluid. This refrigerant contributes to global warming and is expected to be phased out. Consequently, new refrigerants as well as new refrigeration methods need to be developed.
The research detailed in this article attempts to implement the magnetocaloric effect of gadolinium alloy in a designed apparatus to lower the temperature of air. Gadolinium alloy has a noticeable magnetocaloric effect within a strong magnetic field (5 T). This research is aimed at producing a noticeable temperature change (2–3 °C) in a relatively smaller magnetic field (1 T) produced with permanent magnets. This work tests the feasibility of magnetic cooling by introducing the design of a magnetic cooling apparatus, using Gadolinium alloy (Gd5Si2Ge2). Small pebbles were used as opposed to a solid plate in order to have an increased surface area to enhance the convection heat transfer process. Permanent magnets were used in the apparatus, to decrease the operating cost. The maximum temperature change encountered in the heat exchanger of the apparatus built was 2.3 °C in a 1 T magnetic field.
High heat fluxes are encountered in numerous applications, such as on the surfaces of hypersonic vehicles in flight, in fires, and within engines. The calibration of heat flux gauges may be performed in a dual cavity cylindrical blackbody. Insertion of instruments into the cavity disturbs the thermal equilibrium resulting in a transient calibration environment. To characterize the transient heat fluxes, experiments were performed on a dual cavity cylindrical blackbody at nominal temperatures varying from 800°C to 1900°C in increments of 100°C. The pre-insertion, steady state, axial temperature profile is compared experimentally and numerically. Detailed transient thermal models have been developed to simulate the heat flux calibration process at two extreme fluxes: the high flux is 1 MW/m2 and the relatively low is 70 kW/m2. Based on experiments and numerical analysis, the optimum heat flux sensor insertion location as measured from the center partition was determined. The effect of convection (natural and forced) in the blackbody cavity during the insertion is calculated and found to be less than 2% at high temperatures but reaches much higher values at relatively lower temperatures. The transient models show the effect of inserting a heat flux gauge at room temperature on the thermal equilibrium of the blackbody at 1800°C and 800°C nominal temperatures. Also, heat flux sensor outputs are derived from computed sensor temperature distributions and compared with experimental results. The numerical heat flux agreed with the experimental results to within 5%, which indicates that the numerical models captured the transient thermal physics during the calibration. Based on numerical models and all experimental runs the heat transfer mechanisms are explained.
The Senior Mechanical Engineering students at Saint Martin’s College designed and built a unique, safe air conditioning/refrigeration bench experimentation apparatus. The apparatus is currently used as laboratory equipment to support instruction in four thermal engineering courses. This system demonstrates the fundamentals of the refrigeration cycle and psychrometric properties of air, as well as some fundamental concepts in heat transfer, heat exchangers, and thermodynamics. The refrigeration cycle working fluid is R-134a. The cycle operates with pressures between 760 kPa and 210 kPa, and with temperatures between 44 °C and −7 °C with flow rate of 6.8 kg/h. The apparatus is equipped with an instrumentation package to monitor the psychrometric properties of the effected air inside the ductwork. In addition the instrumentation package contains instrumentation to monitor the working fluid properties via computerized data logging equipment. Technical details about the uniqueness of this design and operation are given in the article.
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