Showing papers on "Heat exchanger published in 2014"

Review of High-Temperature Central Receiver Designs for Concentrating Solar Power

Abstract: This paper reviews central receiver designs for concentrating solar power applications with high-temperature power cycles Desired features include low-cost and durable materials that can withstand high concentration ratios (~1000 suns), heat-transfer fluids that can withstand temperatures >650 °C, high solar absorptance, and low radiative and convective heat losses leading to a thermal efficiency >90% Different receiver designs are categorized and evaluated in this paper: (1) gas receivers, (2) liquid receivers, and (3) solid particle receivers For each design, the following information is provided: general principle and review of previous modeling and testing activities, expected outlet temperature and thermal efficiency, benefits, perceived challenges, and research needs Emerging receiver designs that can enable higher thermal-to-electric efficiencies (50% or higher) using advanced power cycles such as supercritical CO 2 closed-loop Brayton cycles include direct heating of CO 2 in tubular receiver designs (external or cavity) that can withstand high internal fluid pressures (~20 MPa) and temperatures (~700 °C) Indirect heating of other fluids and materials that can be stored at high temperatures such as advanced molten salts, liquid metals, or solid particles are also being pursued, but challenges include stability, heat loss, and the need for high-temperature heat exchangers

Thermal management system for vehicle

Abstract: A controller of a thermal management system for a vehicle controls a first switching valve and a second switching valve to set a battery warming-up state in which a heat medium circulates between a battery-temperature adjustment heat exchanger and a heat-medium heating heat exchanger, and the heat medium does not circulate between a coolant-coolant heat exchanger and a heat-medium heating heat exchanger when both a battery and an engine need to be warmed up. In contrast, the controller controls the first switching valve and the second switching valve to set an engine warming-up state in which the heat medium circulates through between the coolant-coolant heat exchanger and the heat-medium heating heat exchanger while the heat medium does not circulate between a battery-temperature adjustment heat exchanger and the heat-medium heating heat exchanger when a temperature of the battery exceeds a target battery warming-up temperature in the battery warming-up state.

A review of frosting in air-to-air energy exchangers

Abstract: Air-to-air heat/energy exchangers are often used with heating or cooling systems in buildings, to transfer heat and moisture from an airstream at a high temperature or humidity to an airstream at a low temperature or humidity. Frosting inside heat/energy exchangers is common in cold regions such as Canada and northern Europe, and results in a significant decrease in the performance of the exchangers. The desire to improve the performance and control strategies of heat/energy exchangers under cold air conditions has led to significant research and development equipment over the past 30 years, however, from an energy savings point of view, this problem has not been researched in as much detail. In this paper, a detailed review of the research on frosting and defrosting techniques, specifically in air-to-air heat/energy exchangers is presented.

Air conditioner and control method thereof

Abstract: The invention belongs to the technical field of air conditioners and aims at solving the problems that a fan is prone to being corroded and huge hidden safety hazards exist when an existing air conditioner is used for performing spraying cooling on an outdoor unit by means of condensate water produced by an indoor unit. To achieve the purpose, the invention provides an air conditioner and a control method thereof. The air conditioner comprises an indoor heat exchanger and an outdoor heat exchanger, and further comprises a water collecting component and a cooling pipe stack communicating with the water collecting component. The cooling pipe stack is arranged on the outdoor heat exchanger or is close to the outdoor heat exchanger. The water collecting component can be used for collecting condensate water produced by the indoor heat exchanger. The cooling pipe stack can be used for cooling the outdoor heat exchanger through the condensate water collected by the water collecting component.The control method comprises the steps that the air conditioner is made to execute a refrigerating mode; the condensate water produced by the indoor heat exchanger is collected; the collected condensate water is conveyed to the cooling pipe stack; and the outdoor heat exchanger is cooled. By means of the air conditioner provided by the invention, the condensate water can be prevented from makingcontact with electrical components such as a fan of an outdoor unit, and therefore, hidden safety hazards are eliminated.

Design Considerations for Supercritical Carbon Dioxide Brayton Cycles With Recompression

Abstract: 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 concentrating solar power (CSP). Two promising SCO2 power cycle variations are the simple Brayton cycle with recuperation and the recompression cycle. The models described in this paper are appropriate for the analysis and optimization of both cycle configurations under a range of design conditions. The recuperators in the cycle are modeled assuming a constant heat exchanger conductance value, which allows for computationally efficient optimization of the cycle’s design parameters while accounting for the rapidly varying fluid properties of carbon dioxide near its critical point. Representing the recuperators using conductance, rather than effectiveness, allows for a more appropriate comparison among design-point conditions because a larger conductance typically corresponds more directly to a physically larger and higher capital cost heat exchanger. The model is used to explore the relationship between recuperator size and heat rejection temperature of the cycle, specifically in regard to maximizing thermal efficiency. The results presented in this paper are normalized by net power output and may be applied to cycles of any size. Under the design conditions considered for this analysis, results indicate that increasing the design high-side (compressor outlet) pressure does not always correspond to higher cycle thermal efficiency. Rather, there is an optimal compressor outlet pressure that is dependent on the recuperator size and operating temperatures of the cycle and is typically in the range of 30–35 MPa. Model results also indicate that the efficiency degradation associated with warmer heat rejection temperatures (e.g., in dry-cooled applications) are reduced by increasing the compressor inlet pressure. Because the optimal design of a cycle depends upon a number of application-specific variables, the model presented in this paper is available online and is envisioned as a building block for more complex and specific simulations. [DOI: 10.1115/1.4027936]