An introduction to heat transfer

The energy performance in buildings is influenced by many factors, such as ambient weather conditions, building structure and characteristics, the operation of sub-level components like lighting and HVAC systems, occupancy and their behavior. This complex situation makes it very difficult to accurately implement the prediction of building energy consumption. This paper reviews recently developed models for solving this problem, which include elaborate and simplified engineering methods, statistical methods and artificial intelligence methods. Previous research work concerning these models and relevant applications are introduced. Based on the analysis of previous work, further prospects are proposed for additional research reference.

A review on the prediction of building energy consumption

Introduction to heat transfer

Optimization Techniques with FORTRAN

Vertical-borehole ground-coupled heat pumps: A review of models and systems

Standing column wells can be used as highly efficient ground heat exchangers in geothermal heat pump systems. This paper describes a computationally efficient numerical model of groundwater flow and heat transfer in and around standing column wells. An approach that utilizes an “enhanced” thermal conductivity to account for the natural groundwater movement, but which explicitly models the induced groundwater flow by “bleed,” is proposed. This model has been validated with experimental data and a reference numerical model (Spitler et al. 2002; Rees et al. 2004; Deng 2004). This simplified model is intended for use in hourly simulation programs or design tools.

http://www.hvac.okstate.edu/sites/default/files/pubs/papers/2005/03-Deng_Rees_Spitler_05.pdf

A Model for Annual Simulation of Standing Column Well Ground Heat Exchangers

Commercial buildings and institutions are generally cooling-dominated and therefore reject more heat to a groundloop heat exchanger than they extract over the annual cycle. This paper describes the development, validation, and use of a design and simulation tool for modeling the performance of a shallow pond as a supplemental heat rejecter in groundsource heat pump systems. The model has been developed in the TRNSYS modeling environment and can therefore be coupled to other GSHP system component models for short time step (hourly or less) system analyses. The model has been validated by comparing simulation results to experimental data collected from two test ponds. The solution scheme involves a lumped-capacitance approach, and the resulting first-order differential equation describing the overall energy balance on the pond is solved numerically. An example application is presented to demonstrate the use of the model as well as the viability of the use of shallow ponds as supplemental heat rejecters in GSHP systems. Through this example, it is shown that ground-loop heat exchanger size can be significantly decreased by incorporating a shallow pond into a GSHP system.

http://www.hvac.okstate.edu/sites/default/files/pubs/papers/2000/04-Chiasson_Spitler_Rees_Smith_00.pdf

A Model for Simulating the Performance of a Shallow Pond as a Supplemental Heat Rejecter with Closed-Loop Ground-Source Heat Pump Systems

Applicability of calculation methods for conduction transfer function of building constructions

This work presents a validation of two common methods for designing vertical ground heat exchangers. Both a simulation-based design tool and the ASHRAE handbook design equation are used to find design lengths for four different real systems, using actual experimental data, including building loads as well as physical parameters as inputs. The measured minimum and maximum ground heat exchanger exiting fluid temperatures were used as the design constraint. The simulation-based design tool predicted the borehole length to within 6% in all cases, while the ASHRAE handbook design equation yielded systems with errors from –21% to 167%. Most of this error can be explained by the way loads are represented in the ASHRAE handbook equation, with differences in the borehole thermal resistance also playing a smaller part. The ASHRAE handbook equation relies on a very simple load representation; although this allows it to be used as a simple hand calculation, it also precludes it achieving acceptable accuracy. It does ...

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Validation of vertical ground heat exchanger design methodologies

Cooling-dominated commercial and institutional buildings served by ground-source heat pump (GSHP) systems generally reject more heat to a closed ground-loop heat exchanger (GLHE) than they extract over the annual cycle. This imbalance may result in a significantly larger GLHE than would be required for a system with annually balanced heat rejection and extraction. So-called “hybrid GSHP systems” use supplemental heat rejecters (such as cooling towers, fluid coolers, cooling ponds, or pavement heating systems) to reject excess heat on a seasonal or diurnal basis, thereby reducing the required size of the GLHE and, hence, the first cost of the system. The design challenge lies in finding the optimum size of both the GLHE and the supplemental heat rejecter, which directly depends upon the control strategy used to reject the excess heat. This study uses a system simulation approach to investigate various design alternatives with the aim of optimally sizing a GLHE with a cooling pond supplemental heat rejecter. A control strategy is selected based on the results of a previous study, and a life-cycle cost comparison is conducted for various design cases in two different climatic regions. This study demonstrates the usefulness of system simulation as a tool for determining the optimal design of hybrid groundsource heat pump systems.

https://www.hvac.okstate.edu/sites/default/files/pubs/papers/2001/01-Ramamoorthy_Jin_Chiasson_Spitler_01.pdf

Jeffrey D. Spitler

Papers

A Model for Annual Simulation of Standing Column Well Ground Heat Exchangers

A Model for Simulating the Performance of a Shallow Pond as a Supplemental Heat Rejecter with Closed-Loop Ground-Source Heat Pump Systems

Applicability of calculation methods for conduction transfer function of building constructions

Validation of vertical ground heat exchanger design methodologies

Optimal Sizing of Hybrid Ground-Source Heat Pump Systems That Use a Cooling Pond as a Supplemental Heat Rejecter— A System Simulation Approach