Papers by Stephen Harrison
Journal of Solar Energy Engineering, 2014
The combination of solar thermal and heat pump systems as a single solar assisted heat pump (SAHP... more The combination of solar thermal and heat pump systems as a single solar assisted heat pump (SAHP) system can significantly reduce residential energy consumption in Canada. As a part of Team Ontario's efforts to develop a high performance house for the U.S. Department of Energy's Solar Decathlon 2013 Competition, an integrated mechanical system (IMS) consisting of a SAHP was investigated. The system was designed to provide domestic hot water (DHW), space-heating, space-cooling, and dehumidification. The system included a cold and a hot thermal storage tanks and a heat pump to move energy from the low temperature reservoir to the hot reservoir. Solar thermal collectors supplied heat to the cold storage and operated at a higher efficiency due to the heat pump reducing the temperature of the collector working fluid. The combination of the heat pump and solar thermal collectors allows more heat to be harvested at a lower temperature, and then boosted to a suitable temperature fo...
Solar Energy, 2013
Thermal stratification in solar energy storage tanks plays an important role in enhancing the per... more Thermal stratification in solar energy storage tanks plays an important role in enhancing the performance of solar domestic hot water systems. The mixing that occurs when hot fluid from the solar collector enters the top of the tank is detrimental to the stratification. Mathematical models that are used for system analysis must therefore be able to capture the effects of this inlet jet mixing in order to accurately predict system performance. This paper presents a computational study of the heat transfer and fluid flow in a thermal storage tank of a solar domestic hot water system with a vertical inlet under negative buoyant plume conditions. The effects of parameters such as the fluid inlet velocity and temperature as well as inlet pipe diameter on the thermal mixing were considered. The work culminated in the development of a one-dimensional empirical model capable of predicting the transient axial temperature distribution inside the thermal storage tank. Predictions from the new model were in good agreement with both experimental data and detailed computational fluid dynamics predictions.
Procedia Computer Science, 2015
The dehumidifier is one of the main components in open-cycle liquid desiccant airconditioning sys... more The dehumidifier is one of the main components in open-cycle liquid desiccant airconditioning systems. An experimental study was carried out to evaluate the performance of a solar thermally driven, low-flow, falling-film, internally-cooled parallelplate liquid desiccant air-conditioner in Kingston, Ontario at Queen's University. A solution of LiCl and water was used as the desiccant. Unlike high-flow devices, the low-flow of desiccant solution flowing across the unit's dehumidifier and regenerator sections produces large variations in solution concentration. In this study, a series of tests were undertaken to evaluate the performance of the dehumidifier section of the unit. Results presented are based on mass flow and energy transport measurements that allowed the moisture transport rate between the air and liquid desiccant solution to be determined. Based on these results, a relationship between the desiccant concentration and the rate of dehumidification rate was found and the effect of inlet-air humidity on the dehumidification effectiveness identified. The moisture removal rate of the system was found to range from 1.1 g/s to 3.5 g/s under the conditions evaluated. These result corresponded to an average dehumidification effectiveness of 0.55.
! I A simple method of comparing the thermal performance of glazing systems is presented. A unive... more ! I A simple method of comparing the thermal performance of glazing systems is presented. A universal performance characteristic can be established for each glazing system, using only its average overall heat-transfer coefficient and shading coefficient. The method also permits the calculation of the net heat gain attainable with a given glazing system. The validity of the assumption of constant window thermal and optical properties is confirmed through comparison with values of net heat gain obtained by detailed calculations using actual hourly atmospheric data for four Canadian locations. The method is extended to permit prediction of the performance of windows using nighttime insulating shutters. An example of its use is given.
This research uses computational fluid dynamics (CFD) to predict the interaction of a natural con... more This research uses computational fluid dynamics (CFD) to predict the interaction of a natural convection driven side-arm heat exchanger with a hot water storage tank. In this paper, a model of a solar domestic hot water tank with vertical compact plate natural convection heat exchanger has been incorporated into the commercial CFD software ANSYS CFX. In order to make the computational solution viable, the fine details of the heat exchanger flow are not calculated directly: the heat exchanger is instead treated as a section of pipe with high flow resistance and with a volumetric energy source. The CFD model is validated by comparison to experimental results from Cruickshank and Harrison (2006).
Journal of Heat Transfer, 2002
The present study examines the influence of heated, horizontal, and rotatable louvers on the conv... more The present study examines the influence of heated, horizontal, and rotatable louvers on the convective and radiative heat transfer from a heated or cooled vertical isothermal surface. The system represents an irradiated Venetian blind adjacent to the indoor surface of a window. Detailed heat transfer results were obtained using a steady, laminar, two-dimensional, conjugate conduction/convection/radiation finite element model for two window temperatures (warm and cool compared to ambient) and irradiation levels, two louver to surface spacings, and three louver angles. The effect of the heated louvers on the heat transfer rate from the surface has been demonstrated.
International Journal of Energy Research, 2006
An approximate method is presented for predicting the effect of a louvered blind on the centre-gl... more An approximate method is presented for predicting the effect of a louvered blind on the centre-glass thermal performance of a fenestration. The method combines a one-dimensional heat transfer model with data from a numerical simulation of the window and blind. Sample results for a blind mounted on the indoor surface of a window show the effect of blind slat angle on heat transmission. Both summer and winter conditions are considered. The results show that a louvered blind can improve the U-value of a standard double-glazed window by up to 37%. Also, the radiation heat exchange with the room can be dramatically reduced (by up to 60%), which will improve the level of occupant comfort. However, there was found to be a trade-off between U-value and occupant comfort; placing the blind closer to the window improves the U-value, but increases the radiation heat exchange with the room. The predictions from the present simplified method compare well with results from a full two-dimensional computational fluid dynamics solution of the conjugate blind/window interaction.
Applied Energy, 2013
h i g h l i g h t s " A multi-tank system was evaluated under three charge and discharge configur... more h i g h l i g h t s " A multi-tank system was evaluated under three charge and discharge configurations. " Constant temperature charging and constant volume draws were performed. " Charging in series resulted in sequentially stratified tanks. " Discharging in series resulted in mixing at the bottom of the upstream tanks. " Discharging in parallel maintained a high degree of stratification in each tank.
Solar Energy, 2005
ABSTRACT The interior surfaces of heat exchangers used in domestic hot water systems are particul... more ABSTRACT The interior surfaces of heat exchangers used in domestic hot water systems are particularly prone to fouling or complete blockage due to the accumulation of sediments, scale and mineral deposits. In many locations, mineral salts and other impurities may be present in the potable water supply and fouling may occur if the heat exchanger is not routinely cleaned or flushed of accumulated matter. In small residential installations, however, this is not practical due to the associated costs. In response to this need, a passive back-flushing system was designed that allows heat exchangers to be routinely back-flushed many times a day. The action is a normal operation of the system and does not require user intervention, external power or controls to function. During back-flushing mineral deposits are washed out of the heat exchanger and flushed from the system. the operation of the device and documents the results of accelerated tests undertaken to verify its operation.
Proceedings of the ISES Solar World Congress 2011, 2011
This paper presents an experimental comparison of two common heat exchanger configurations used i... more This paper presents an experimental comparison of two common heat exchanger configurations used in residential-sized solar water heating systems to evaluate the relative merits and effects of heat exchanger placement (in-tank immersed coil versus external thermosyphon heat exchanger) on storage tank temperature profiles. Experiments were conducted on a specialized test apparatus that allowed controlled charge sequences to be studied for the two configurations considered. The results of this study provide a significant insight into the operation of indirect solar systems configured with immersed coil, or external, heat exchangers and their effect on tank stratification levels. Test results were evaluated on both a First and Second Law Thermodynamic basis, illustrating differences in temperature profiles, energy and exergy levels occurring after identical charge sequences. Results of these tests indicate that, for the configurations studied, higher tank temperatures, stratification and exergy levels were achieved earlier in the charge sequence with the external thermosyphon heat exchanger than with the immersed coil heat exchanger. In addition, it was observed that charging of a partially stratified storage with an immersed coil can result in tank mixing, resulting in a reduction in the temperature and exergy level of the stratification layer
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Papers by Stephen Harrison