This thesis evaluates the effects of Combined Heating and Power (CHP) systems with a Propane fueled spark ignited engine as prime mover used in a small commercial building. The system was evaluated in five different U.S. cities. The most common operating modes, thermal load following (FTL) and electric load following (FEL) were evaluated, and an optimized operating mode was developed and investigated. The optimized operating mode is a hybrid (FHL) of FEL and FTL operation. Methodology for the derivation and application of these models is presented. Also, the economic effects of Diesel and Natural Gas were investigated. The results for all five cities and all three operating modes were gathered and compared with a conventional system. Comparisons were made based on cost, primary energy consumption, and carbon dioxide emissions. It was concluded that the feasibility of CHP had great potential, but is highly dependent upon the location of the system.

No description available.

A novel concept of recovering heat from hot gases using countercurrently flowing vibrofluldized solids (that is, solids levitated solely by mechanical vibration) has been proposed and tested. Based on a theoretical heat transfer model, the heat transfer coefficient between the air and the solids was calculated. A factorial design of experiments showed that a higher heat transfer coefficient was obtained with higher air flow rates and lower solid flow rates. The baffle height had an insignificant affect on the heat transfer. Tests with multiple baffles led to a maximum heat transfer coefficient (143 W/m²-K) when using four baffles. For all tests performed in this work, the solids were not truly vibrofluldized. Instead, they were merely vibro-conveyed (or vibro-shuffled) as a single mass. A new vibrating system will provide the sufficient energy for vibrofluidization, and enhanced heat transfer is expected. This work demonstrated for the first time the solid impeding phenomenon in a fluidized-bed heat exchanger. Specifically, experimental tests showed that if a baffle was lowered past a limiting height at given air and solid flow rates, the increased air velocity past a baffle could prevent the solids from exiting the exchanger. An economic evaluation showed that the vibrofluidized-bed heat-exchanger system would be economically feasible for the production of boiler feedwater using heat recovered from boiler combustion gases. The payback time for the system could be as little as 1.4 years. The convective heat-transfer data from a supernatant gas to a flowing vibrofluidized bed of solids were the first of their kind, and they have led to a better understanding of the new vibrofluidized-bed heat-exchanger system. The successful completion of this project sheds encouraging light onto future heat-recovery operations with such a system. / Master of Science

A novel concept (called “heat tray”) is proposed for heat recovery from hot gases and for heat management in exothermic catalytic reactions, which involves a supernatant gas (S-gas) flowing over a shallow fluidized bed of solids. This thesis presents the results of bench-scale and pilot-scale experimental studies that quantify heat transfer between the S-gas and the shallow fluidized bed. A fractional-factorial design of experiments was performed on two heat-tray systems using three different results showed that fine fluid cracking catalyst (FCC) particles out-performed larger alumina spheres as a fluidized solid. Heat transfer coefficients between the supernatant gas and the shallow fluidized bed approached 440 W/m²-K using FCC. Various S-gas inlet nozzle configurations were studied, with a nozzle height equal to one-half of the static bed height (0.051 m) giving the best results. The study showed that short heat-tray lengths (<0.8 m) are desirable and that S-gas redistributors are needed to compartmentalize the unit. An economic analysis showed that the proposed heat tray would be economically feasible for adaption as a boiler feedwater preheater in a small steam-generation facility, using boiler combustion gases as the S-gas. The payback time for the system would be as short as 1.9 years when used continuously. The heat transfer results from a S-gas to a flowing shallow fluidized bed represent the only data reported thus far, and have led to a better understanding of the new shallow fluidized-bed system for heat-exchange applications. / Master of Science

Heating, ventilation and air-conditioning (HVAC) systems are widely distributed over the world due to their capacity to adjust some local climate parameters, like temperature, relative humidity, cleanliness and distribution of the air until the desired levels verified in a hypothetical ideal climate. A review of buildings’ energy usage in developed countries shows that in the present this energy service is responsible for a portion of about 20% of the final energy usage on them, increasing up to 50% in hot-humid countries. In order to decrease this value, more and more different heat recovery systems have been developed and implemented over the last decades. Nowadays it is mandatory to install one of these units when the design conditions are above the limit values to avoid such components, what is possible to verify mostly in non-residential buildings. Each one of those units has its own performance and working characteristics that turns it more indicated to make part of a certain ventilation system in particular. Air-to-air energy recovery ventilation is based on the heat recovery transfer (latent and/or sensible) from the flow at high temperature to the flow at lower temperature, pre-warming the outdoor supply air (in the case of the winter). Therefore, it is important to understand in which concept those units have to be used and more important than that, how they work, helping to visualize their final effect on the HVAC system. The major aims of this study were to investigate the actual performance of the heat recovery units for LB20 and LB21 in building 99 at the University of Gävle and make some suggestions that could enhance their actual efficiency. Furthermore, the energy transfer rates associated to the heat recovery units were calculated in order to understand the impact of such components in the overall HVAC system as also the possible financial opportunity by making small improvements in the same units. To assess the system, values of temperature and flow (among others) were collected in the air stream and in the ethylene-glycol solution that works as heat transfer medium between air streams and is  enclosed in pipes that make part of the actual run-around heat recovery units. After some calculations, it was obtained that for the coldest day of measurements, the sensible effectiveness was 42% in LB20 and 47% in LB21, changing to 44% and 43% in the warmer day, respectively. The actual heat transfer representing the savings in the supply air stream is higher on the coldest day, with values of 46 kW in LB20 and 84 kW in LB21, justifying the existence of the heat recovery units even if those ones imply the use of hydraulic pumps to ensure the loop. The low values of efficiency have shown that both heat recovery units are working below the desired performance similarly to the pumps that make part of the same units.  This fact, together with the degradation of the units that is possible to observe in the local, indicates that a complete cleaning (followed by a change of the heat transfer medium) of the heat recovery units and a new adjustment of pumps and valves for the further changes, are necessary. By doing this, it is expected to see the year average sensible effectiveness increase to close to 45% in both units which will lead to a potential economic saving of around 41 000 SEK per year.

The purpose of this thesis is to experimentally determine the feasibility of an ejector based, waste heat recovery driven refrigeration system applied to the data center environment in order to reduce operational cooling costs. A comprehensive literature review is detailed to determine the current state of the ejector refrigeration research and assess the initial direction of this thesis. A simplified model was created to perform preliminary performance estimations and system sizing before constructing an experimental system apparatus to evaluate the model predictions. The pressures and temperatures used in the model and instituted in the experimental system are based on the maximum temperatures typically observed in computing servers (50-75°C). Precision controlled heaters are used to simulate the computer server heat, and R245fa is used as the working fluid. Performance results ranged from 0.06 to 0.13.

The development and implementation of technologies that improves Heating Ventilation & Air Conditioning (HVAC) system efficiency, including unique waste heat recovery methods, are sought while considering financial constraints and benefits. Recent studies have found that through the use of advanced waste heat recovery systems, it is possible to reduce building’s energy consumption by 30%. Oscillating heat pipes (OHP) exists as a serpentine-arranged capillary tube, possesses a desirable aerodynamic form factor, and provides for relatively high heat transfer rates via cyclic evaporation and condensation of an encapsulated working fluid with no internal wicking structure required. In last two decade, it has been extensively investigated for its potential application in thermal management of electronic devices. This dissertation focuses on the application of OHP in waste heat recovery systems. To achieve the goal, first a feasibility study is conducted by experimentally assessing a nine turn copper-made bare tube OHP in a typical HVAC ducting system with adjacent air streams at different temperatures. Second, for a prescribed temperature difference and volumetric flow rate of air, a multi-row finned OHP based Heat Recovery Ventilator (OHP-HRV) is designed and analyzed for the task of pre-conditioning the intake air. Additionally, the energy and cost savings analysis is performed specifically for the designed OHP-HRV system and potential cost benefits are demonstrated for various geographical regions within the United States. Finally, an atypically long finned OHP is experimentally investigated (F-OHP) under above prescribed operating condition. Helical fins are added to capillary size OHP tubes at a rate of 12 fins per inch (12 FPI), thereby increasing the heat transfer area by 433%. The coupled effect of fins and oscillation on the thermal performance of F-OHP is examined. Also, F-OHP’s thermal performance is compared with that of bare tube OHP of similar dimension and operating under similar condition. It was determined that OHP can be an effective waste heat recovery device in terms of operational cost, manufacturability, thermal and aerodynamic performance. Moreover, it was also determined that OHP-HRV can significantly reduce energy consumption of a commercial building, especially in the winter operation.

No description available.

Call number: LD2668 .T4 1978 O86 / Master of Science

Call number: LD2668 .T4 1978 S24 / Master of Science