Development of a methodology for an optimal design of a district cooling distribution network

Date of Publication

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering

College

Gokongwei College of Engineering

Department/Unit

Mechanical Engineering

Thesis Adviser

Alvin B. Culaba

Defense Panel Chair

Archie B. Maglaya

Defense Panel Member

Jose Bienvenido Manuel M. Biona
Renan Ma. T. Tanhueco
Alma Bella P. Madrazo
Dominic C.Y. Foo

Abstract/Summary

One of the most expensive portions of a large-scale cooling system is the distribution network that conveys the chilled water serving multiple buildings for use in space cooling. As the piping network requires large initial investment cost, careful design is needed to optimize its use. Proper identification of design criteria would be required to determine the minimum overall costs of construction and maintenance of piping system. In order to come up with the solution a methodology for an optimal design of district cooling distribution network was developed.

In this study, the hydraulic calculation and system simulation of distribution network with and without secondary lines are presented. The theoretical system pressure drop, system flow rate and flow rate requirements in each energy transfer station were determined considering a desired temperature difference set-point. Variable primary flow of chilled water pumping arrangement was used as basis for fluid flow analysis to improve energy usage and to eliminate the need for a separate distribution pump in the network.

Pipe sizing and friction factor identification were necessary to determine the frictional coefficients of distribution network components. Implicit Colebrook-White equation was used to determine the pipe friction factor. The method of Least Squares and Cholesky decomposition method were also adopted to derive new set of pump characteristic curve considering that pumps are modulated at its best efficiency points. The governing equations consisted of mass conservation and energy equations in the form of pump characteristic curve and distribution network characteristics. The system of nonlinear equations was solved using multivariable Newton-Raphson method. The linearized equations revealed that coefficient matrices formed between two networks were different from each other which suggested that different decomposition algorithms must be used to ensure the solution vectors are properly determined. Distribution networks with and without secondary lines showed that Jacobian matrix can be solved using singular-value decomposition and LU decomposition methods, respectively. The results of system characteristic curve which indicated the best efficiency points during selected part load and full load conditions.

An optimization technique using exhaustive search method was adopted to determine the piping network design criteria that could give minimum overall costs of construction and maintenance of piping system. Numerical results show that distribution network with secondary lines yields minimum overall costs as compared with piping network without secondary line considering that nominated loads, pipe lengths and fittings, normalized annual power load demand factor and costs parameters associated with components of objective function are held constant.

Abstract Format

html

Language

English

Format

Electronic

Accession Number

CDTG006355

Shelf Location

Archives, The Learning Commons, 12F Henry Sy Sr. Hall

Physical Description

computer optical disc.

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