Narrow Results

In order to investigate the feasibility of the direct ice slurry transporting system for the purpose of district cooling, a case study of field application is performed. The research aims to include the field measurement of ice packing factor, the performance of cold energy delivery, and the branching characteristics of ice slurry in which the additive is propylene glycol wt 10%. Two representative types of pipe branch are dealt with in this work. For the slurry flow with ice volume fraction of 0.16 or less, the pipe blocking due to aggregation is not observed. It is confirmed that the mass flow rate of ice slurry per unit cooling load markedly decreases with the increase of the ice content. The pumping power also decreases, but remains unchanged when the ice fractions are higher than a certain level.

Reduction effect of greenhouse gas emissions from district cooling system by using waste heat from a cogeneration plant has received specific attention from the perspective of national energy and environmental policy, and was studied in this work. For each cooling system of a residential and commercial building, greenhouse gas emissions was estimated and compared to quantify reduction effect on emissions where the heat source of heat-powered cooling system was replaced with a cogeneration waste heat. In addition, to address the problem that the values of waste heat and CEF vary depending on variables such as national or geographical conditions, a general-purpose criterion to measure the utility of substituting a district cooling for a conventional system was suggested.

Energy consumption and its associated consequences can be reduced by implementing district cooling strategies that supply low temperature water to a wide range of end users through chillers and distribution networks. Adequate understanding, performance prediction and further optimization of vapor compression chillers used widely in district cooling plants have been a subject of intense research through model-based approaches. In this context, we perform an extensive review of different modeling techniques used for predicting steady-state or dynamic performance of vapor compression liquid chillers. The explored modeling techniques include physical and empirical models. Different physical models used for vapor compression chillers, based on physics laws, are discussed in detail. Furthermore, empirical models (based on artificial neural networks, regression analysis) are elaborated along with their advantages and drawbacks. The physical models can depict both steady- and unsteady-state performance of the vapor compression chiller; however, their accuracy and physical realism can be enhanced by considering the geometrical arrangement of the condenser and evaporator and validating them for various ecofriendly refrigerants and large system size (i.e., cooling capacity). Apparently, empirical models are easy to develop but do not provide the necessary physical realism of the process of vapor compression chiller. It is further observed that DC plants/networks have been modeled from the point of view of optimization or integration but no efforts have been made to model the chillers with multiple VCR cycles. The development of such models will facilitate to optimize the DC plant and provide improved control strategies for effective and efficient operation.