Although water-cooled chillers are more energy efficient than air-cooled chillers, a majority of chilled water systems use air-cooled chillers. In cold weather climates, air-cooled chillers are capable of functioning in low ambient temperatures with few operational concerns, where as water-cooled chiller systems must be equipped to prevent cooling tower freezing. The integrated chiller system a...

Water-cooled chiller systems have typically been designed around entering condenser water temperatures of 85°F with a Optimization of Water Cooled Chiller – Cooling Tower Combinations The warm water leaving the chilled water coils is pumped to the evaporator of the chiller, where the unwanted heat from the building is transferred by the latent heat of vaporization of the refrigerant. The compre...

This study constructed a parameter analysis for improving the energy performance of air-cooled water chillers by altering the angle configuration of the condenser coils. The mathematical models for energy and exergy analyses of the individual components and overall system of air-cooled water chillers are presented. This study investigated the potential enhancement of performance efficiency in a...

During extremely hot summer days, air conditioning systems are known as major electricity consumers in residential, commercial and industrial sectors. Moreover, high energy requirement of multiple-chiller plants may cause an interconnected power grid be faced with annual on-peak electrical demand, load-generation mismatch, voltage collapse and catastrophic wide area blackout. Therefore, this pa...

The operation of air-cooled chillers accounts for significant energy consumption in local commercial buildings, and low operational efficiency especially under partial load conditions and poor control are part of reasons for such huge energy consumption. Chiller efficiency can be improved by enhancing heat transfer rate in condensers. This paper considers how the chiller performance can be impr...

A steady-state model for a centralized cooling system is developed to enable proper provisioning of cooling resources in capital intensive projects such as data centers. The model resolves the energy equations for a cooling tower and a centralized water-cooled chiller simultaneously. It requires inputs that are readily available to the design engineer. The user inputs are the ambient conditions...

For simulation of centrifugal chiller system with differential algebraic equations (DAEs), consistent initial conditions are difficult to obtain due to the two-phase refrigerant cycle and the connections between several components. Existing rigorous initialization methods are generally not easy to apply and not suitable for the particular problem of centrifugal chiller simulation, such as the s...

In this paper, the transient model of a water-cooled centrifugal chiller is developed in Modelica with Dymola and the TLK/IfT Library (TIL). The centrifugal compressor is modeled in detail based on the turbomachinery theory. The chiller capacity control is achieved by the combination of variable inlet guide vane (VIGV) and variable speed drive (VSD). The shell-and-tube heat exchangers are discr...

A dynamic model for the simulation of a new single-effect water/lithium bromide absorption chiller is developed. The chiller is driven by two distinct heat sources, includes a custom integrated falling film evaporator-absorber, uses mixed recirculation and is exclusively cooled by the ambient air. Heat and mass transfer in the evaporator-absorber and in the desorber are described according to a...

The chilled-water systems, mainly consisting of electric chillers and cooling towers, are crucial for the ventilating and air conditioning systems in commercial buildings. Energy efficient operation of such systems is thus important for the energy saving of commercial buildings. This paper presents an extremum seeking control (ESC) scheme for energy efficient operation of the chilled-water syst...