Sanford A Klein

University of Wisconsin–Madison | UW · Department of Mechanical Engineering

A thermal response test (TRT) is commonly conducted at a site proposed for the installation of a ground-coupled heat pump system. The purpose of the TRT is to gather local data to infer thermal properties of the soil. Accurately estimating soil thermal properties enables designers to size the geofield appropriately and supports improved simulations...

The NIST Net-Zero Energy Residential Test Facility (NZERTF) is a highly instrumented, highly configurable, single-family, net-zero energy house occupied by a virtual family of four. A detailed transient model of the NZERTF and the accompanying mechanical equipment was created using information available before construction; the model incorporated b...

This paper presents a new method called the Crossed Contour Method for determining the effective properties (borehole radius and ground thermal conductivity) of a vertical ground-coupled heat exchanger. The borehole radius is used as a proxy for the overall borehole thermal resistance. The method has been applied to both simulated and experimental...

Zeotropic mixtures are widely used in mixed refrigerant Joule–Thomson cryocoolers for various applications such as cryoprobes. Within the Joule–Thomson cycle, multicomponent mixtures exist in a two-phase condition throughout a large portion of the system. Frictional pressure drop correlations for zeotropic refrigerants operating at these conditions...

The use of mixed gas working fluids has become common in Joule–Thomson type cryocoolers for a variety of applications. However, there is a scarcity of data currently available with supporting theory capable of predicting the heat transfer coefficients associated with two-phase, multi-component mixtures at cryogenic temperatures. This paper aims to...

The use of near-ambient pressure air as the heat transfer fluid in central receiver concentrating solar power (CSP) plants operating the water/steam cycle presents a number of potential benefits that have attracted research attention to the concept. In such plants, an open volumetric solar receiver (OVR) is used to heat air entrained from the atmos...

There is a scarcity of data and theory currently available regarding the heat transfer coefficients associated with two-phase, multi-component mixtures at cryogenic temperatures. This paper presents results of research aimed at measuring theconvection heat transfer coefficients for hydrocarbon mixtures (methane, ethane, propane, and nitrogen (for d...

This paper describes an experimental facility designed and constructed to measure the heat transfer coefficients and frictional pressure drop in a small diameter, horizontal test section with two-phase, multi-component zeotropic mixtures at cryogenic temperatures. The aim of this facility is to enable the collection of high accuracy data to overcom...

Supercritical CO 2 ( sCO 2 ) is a promising working fluid for future high-efficiency power conversion cycles. In order to develop these cycles, it is necessary to understand supercritical and two-phase CO 2 flow. This paper presents a methodology for the computational fluid dynamic (CFD) simulation of sCO 2 flowing through a restriction under a wid...

Supercritical carbon dioxide (SCO2) Brayton cycles have the potential to offer improved thermal-to-electric conversion efficiency for utility scale electricity production. These cycles have generated considerable interest in recent years because of this potential and are being considered for a range of applications, including nuclear and concentrat...

Current models of Active Magnetic Regenerative Refrigeration (AMRR) cycles are not able to capture the effect of magnetic hysteresis and are therefore strictly limited to second order magnetic transition (SOMT) materials. The discovery of the giant magnetocaloric effect (GMCE) in first order magnetic transition (FOMT) materials has generated substa...

This paper describes the methods used to measure flow rate of supercritical and two-phase CO2 through short orifices. Orifices with diameters of 1 millimeter and orifice length-to-diameter ratios of 3.2 and 5 were tested. Flow rates through these orifices were measured over a broad range of inlet conditions in the supercritical region with orifice...

Continuing efforts to increase the efficiency of utility-scale electricity generation has resulted in considerable interest in Brayton cycles operating with supercritical carbon dioxide (S-CO2). One of the advantages of S-CO2 Brayton cycles, compared to the more traditional steam Rankine cycle, is that equal or greater thermal efficiencies can be r...

This book differs from other thermodynamics texts in its objective which is to provide engineers with the concepts, tools, and experience needed to solve practical real-world energy problems. The presentation integrates computer tools (e.g., EES) with thermodynamic concepts to allow engineering students and practising engineers to solve problems th...

This paper describes a general method to calculate the semi-gray radiation heat transfer that occurs within an enclosure comprised of diffuse surfaces. The method is implemented in an existing solar power tower cavity receiver model in the System Advisor Model (SAM, NREL, 2011). The semi-gray radiation model is used to find an optimal distribution...

Cryosurgery is a medical technique that uses a cryoprobe to apply extreme cold to undesirable tissue such as cancers. Precooled Mixed Gas Joule-Thomson (pMGJT) cycles with Hampson-style recuperators are integrated with the latest generation of cryoprobes to create more powerful and compact instruments. Selection of gas mixtures for these cycles is...

Losses within a pulse tube cryocooler (PTC) are dominated by regenerator losses that scale directly with the magnitude of the mass flow rate within the regenerator. Therefore, in order to maximize PTC performance it is necessary to minimize the ratio of the mass flow rate in the regenerator to the acoustic power. This is accomplished by controlling...

The temperature of a photovoltaic module is typically required as an input to models that predict the module’s performance. Some common models use the nominal operating cell temperature (NOCT), as by the manufacturer. This paper develops a thermal model and uses it to analyze NOCT testing standards. Specifically, the standard correction factor char...

Hybrid ground source heat pump (HyGSHP) systems are gaining popularity as a means of decreasing long term energy and maintenance costs while maintaining manageable first costs. In these systems there is a potential to use the ground not only as an immediate heat source or sink, but also as an energy store. On a scale of months, heat rejected to the...

The “five-parameter model” is a performance model for photovoltaic solar cells that predicts the voltage and current output by representing the cells as an equivalent electrical circuit with radiation and temperature-dependent components. An important feature of the five-parameter model is that its parameters can be determined using data commonly p...

This article presents an investigation on the impact of year-to-year weather variability on the optimal design of a system for heating and cooling a building using a ground-source heat pump. The designs of a boiler–ground-source heat pump hybrid and a cooling tower–ground-source heat pump hybrid were optimized using a typical meteorological year (T...

This article provides an overview of short time-scale validation of the duct storage model (Hellström 1989) for the simulation of ground source heat pump performance using experimental data acquired from two operational systems. The error in the temperature change across the ground heat exchanger in the first system was within measurement error, bu...

A two-dimensional finite element model describing the performance of parallel-plate regenerators with arbitrary channel width distributions has been developed in order to investigate the effect of non-uniform plate spacing on the performance of regenerators. Results for a series of hypothetical plate spacing distributions are presented in order to...

This paper provides an assessment of the large-scale implementation of distributed solar photovoltaics in Wisconsin with regard to its interaction with the utility grid, economics of varying levels of high penetration, and displaced emissions. These assessment factors are quantified using simulations with measured hourly solar radiation and weather...

This paper reports on a micromachined Si/glass stack recuperative heat exchanger with in situ temperature sensors. Numerous high-conductivity silicon plates with integrated platinum resistance temperature detectors (Pt RTDs) are stacked, alternating with low-conductivity Pyrex spacers. The device has a 1 ?? 1-cm² footprint and a length o...

This paper reports on design, fabrication, and testing of a piezoelectrically actuated microvalve with integrated sensors for flow modulation at low temperatures. One envisioned application is to control the flow of a cryogen for distributed cooling with a high degree of temperature stability and a small thermal gradient. The valve consists of a mi...

The operation of solar energy systems is necessarily transient. Over the lifetime of a concentrating solar power plant, the system operates at design conditions only occasionally, with the bulk of operation occurring under part-load conditions depending on solar resource availability. Credible economic analyses of solar-electric systems requires ve...

This paper investigates the sensitivity of the long-term performance simulations of solar energy systems to the degree of stratification in both liquid and packed-bed storage units. The degree of stratification is controlled by the number of nodes used in a finite-difference approximation of the storage system temperature distribution. Short- and l...

This paper reports a micromachined recuperative heat exchanger integrated with in-situ temperature sensors. In this design, numerous high-conductivity silicon plates, integrated with platinum resistance temperature detectors (Pt RTDs) are fabricated and stacked alternating with low- conductivity Pyrex spacers. The device is intended for use with Jo...

This textbook provides engineers with the capability, tools and confidence to solve real-world heat transfer problems. It includes many advanced topics, such as Bessel functions, Laplace transforms, separation of variables, Duhamel's theorem and complex combination, as well as high order explicit and implicit numerical integration algorithms. These...

"This paper reports on a normally open piezoelectrically actuated microvalve for high flow modulation at cryogenic temperatures. One application envisioned is to control the flow of a cryogen for distributed cooling with a high degree of temperature stability and a small thermal gradient. The valve consists of a micromachined die fabricated from a...

This paper describes a steady numerical flow model and experimental gas flow results of a self-encapsulated, piezoelectrically actuated, cryogenic micro-valve for distributed cooling applications. Experimental flow data of the prototype micro-valve design is obtained for various gases at room temperature and for helium at near liquid nitrogen tempe...

This paper reports on a drug delivery system that provides modulated delivery of liquid-phase chemicals. The device uses silicon torsion springs on a 2times3 cm² chip to pressurize a soft polymeric reservoir and regulate flow with a piezoelectricaly actuated silicon microvalve that is 1.5times1.5times1 cm³. Using the finished...

Active magnetic regenerative refrigeration (AMRR) systems represent an environmentally attractive alternative to vapor compression systems that do not use a fluorocarbon working fluid. The AMRR concept has previously been demonstrated using superconducting solenoid magnets that are not practical for small-scale commercial applications. However, rec...

This paper describes results from two types of micromachined recuperative heat exchangers intended for Joule-Thomson (J-T) cryosurgical probes, which require high stream-to-stream thermal conductance while restricting parasitic stream-wise (axial) conduction. In design A, rows of fins composed of high conductivity silicon are bonded onto a 100 mum...

Active magnetic regenerative refrigeration (AMRR) systems represent an environmentally attractive refrigeration alternative that does not use a fluorocarbon working fluid. Recently, families of magnetocaloric material alloys with adjustable Curie temperatures have been developed. Using these materials, it is possible to construct a layered regenera...

A cryosurgical probe is a medical instrument that is designed to kill cancerous tissue by exposure to cryogenic temperatures. The most important figure of merit for a cryosurgical probe of fixed size is the dimension of the cryolesion that can be generated within a specified time during a surgical procedure. The optimization of the cryoprobe, throu...

Entrained fluid heat capacity is shown to have a significant and positive effect on the performance of a passive regenerator. The ineffectiveness of the regenerator is presented as a function of three dimensionless parameters: the number of transfer units, the utilization, and the entrained fluid to matrix heat capacity ratio. Three different behav...

Solar radiation data are available for many locations on an hourly basis. Simulation studies of solar energy systems have generally used these hourly values to estimate long-term annual performance, although solar radiation can exhibit wide variations during an hour. Variations in solar radiation during an hour, such as on a minute basis, could res...

Hybrid solar lighting (HSL) systems distribute natural sunlight to luminaires located in office or retail buildings in order to reduce energy consumption associated with conventional lighting systems. HSL systems reduce energy consumption directly by reducing the lighting energy and indirectly by reducing the associated cooling loads. A key compone...

Mixed gas working fluids can be used within Joule-Thomson devices to achieve a greater refrigeration effect than is possible with a pure substance. Lower temperatures and higher cooling powers can be obtained with appropriate mixtures, resulting in lower operating pressures and mass flow rates. This paper describes a computational tool that allows...

Electrical leads used for the supply of current to superconducting magnets and electronics must span the temperature range from room temperature to cryogenic temperatures. Because the conventional materials used for such purposes (e.g., copper and aluminum) have both a finite electrical resistance and a significant thermal conductivity, operation o...

The clearness index for hourly and daily radiation is an important parameter in describing solar radiation. Liu and Jordan demonstrated that the monthly average daily clearness index could be used to predict the long-term distribution of daily solar radiation in a month. This paper reviews recent literature on the prediction of hourly and daily fre...

The performance of an air breathing proton exchange membrane (PEM) fuel cell stack has been experimentally measured to investigate the steady-state and transient effects of temperature, humidity and air flowrate. The results show that hydrogen leaks to the cathode through the membrane causing internal heating of the fuel cell. The leakage rate is f...

The clearness index for hourly and daily radiation is an important parameter in describing solar radiation. Liu and Jordan demonstrated that the monthly average daily clearness index could be used to predict the long-term distribution of daily solar radiation in a month. This paper reviews recent literature on the prediction of hourly and daily fre...

The extended corresponding states (ECS) model of Huber et al. (Huber M.L., Friend, D.G., Ely, J.F. Prediction of the thermal conductivity of refrigerants and refrigerant mixtures, Fluid Phase Equilibria 1992;80:249-61) for calculating the thermal conductivity of a pure fluid or fluid mixture is modified by the introduction of a thermal conductivity...

This paper investigates the benefits of using two separate refrigeration cycles to meet demands for both the freezer and fresh food compartments in domestic refrigerators. The energy savings that can be obtained by delivering refrigeration at the higher temperature as required by the fresh food compartment is found to be a function of the cabinet l...

A combined feedback and feedforward algorithm is explored for use in local HVAC control systems. A simple yet effective general regression neural network is suggested in order to identify the characteristics of the HVAC components and for subsequent use in the feedforward algorithm. Simulated results show that the combined controller can perform ex...

A simple yet effective general regression neural network (GRNN) paradigm is suggested for heating, ventilating, and air-conditioning (HVAC) control applications. Unlike the popular backpropagation paradigm, the proposed GRNN is simple to implement, requires only one parameter, and works well with sparse and random data. A simple local HVAC control...

The laboratory heat load is a significant contributor of internal heat gains. The heat load is usually generated by instrumentation, experimental equipment, furnaces, etc. The sensible to total heat ratio in laboratories is high. The magnitude of heat load varies from laboratory to laboratory. In addition, the rate of heat generation may be rapid a...

A steady-state computer simulation model of a direct-fired double-effect water-lithium bromide absorption chiller in the parallel-flow configuration was developed from first principles. Unknown model parameters such as heat transfer coefficients were determined by matching the model's calculated state points and coefficient of performance (COP) aga...

A physiologically based objective function for identifying a combination of ferromagnetic seed temperatures and locations that maximizes the fraction of tumor cells killed in pretreatment planning of local hyperthermia. An objective-function is developed and coupled to finite element software that solves the bioheat transfer equation. The sensitivi...

The five computer programs TRNSYS, PRESIM, TRNSED, ONLINE and PREBID have been put together into a program package which is the most complete solar energy system modeling and simulation software that is available today.

The popularity, user-friendliness, and accessibility of personal computers encourages their use as powerful computational tools for numerical and graphical aids in the visualization of concepts that may seem abstract to students. Methods are presented for using the Apple MacIntosh computer for the numerical solution and mapping of fields for electr...

The current state of development of passive solar design tools is reviewed. The advantages and disadvantages of simulation and correlation methods are discussed. A bibliography is provided which lists most of the design tools developed or used by the solar community.

This paper describes TRNSYS, a computer program designed specifically to connect component models in a specified manner, solve the simultaneous equations of the system model, and display the results. Solar energy system components are described by individual FORTRAN subroutines. These subroutines comprise a growing library of equipment models avail...

Aus den Aminen (I) werden die Sulfonimide (II) hergestellt, die mit nucleophilen Reagentien die Imidgruppe eliminieren.

Aus Aminen (I) und Sulfonsäurechloriden (II) hergestellte Sulfonamide (III) werden mit NaH in DMF in die Salze (IV) umgesetzt werden.

A simple two-step derivatization procedure for the preparation of a variety of N-alkyl-NN- disulfonimides (2) from the parent amines and sulfonyl chlorides is presented. Yields of up to 99% have been obtained. The diarylsulfonimides 2 are in general stable, crystalline solids. The synthetic procedure was developed since these compounds have been ob...

The TRNSYS [1] program provides algorithms to calculate the beam and diffuse radiation on any surface as a function of time based on horizontal radiation measurements. However, no methods are currently provided in TRNSYS to determine the spectral distribution of solar radiation. This paper describes the inclusion of a spectral model in TRNSYS. The...

Existing analytical models to determine the collector heat removal factor for serpentine collectors have limitations both for low flow and a large number of tube bends. A finite-dif-ference numerical model was compared to existing analytical models (Abdel-Khalik, 1976 and Zhang & Lavan, 1985). The finite difference model shows that if the serpentin...

There has been some debate between researchers as to whether optimum flow rates exist in a solar domestic hot water system utilizing a heat exchanger between the collec-tor and the storage tank. It was found that there exists thermal optimum or at least economical optimum flow rates since low flow rates incur less hydraulic costs. Peak performance...

This paper describes a proportional valve that regulates viscous liquid media, intended for use with elastic reservoir/pumps in a portable drug delivery system. The valve is fabricated in a partially open state to permit flow even in the absence of applied power. At room temperature, piezoelectric actuation from -30 V to 60 V causes modulation of o...

This paper describes a normally-open, self-encapsulated, valve for modulating refrigerant flow in a cryogenic cooling system. The valve consists of a micromachined die fabricated from a silicon-on-insulator wafer and a glass wafer, a commercially available piezoelectric stack actuator, and Macor ceramic encapsulation that has overall dimensions of...

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