Thermal Analysis of Hollow Core Ventilated Slab Systems

Park, Benjamin

Graduate Thesis Or Dissertation

Thermal Analysis of Hollow Core Ventilated Slab Systems Public Deposited

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Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/6w924c09n

Abstract

Hollow core ventilated slab systems actively utilize building thermal mass through air channels inside precast floor slabs to meet heating and cooling needs in the space. Various configurations of hollow core ventilated slab systems have been employed in northern/western Europe, Australia, and the Middle East. Compared to conventional air systems, hollow core slab systems offer better thermal comfort, reduced energy consumption for heating and cooling, and improved ventilation control. Most of the models reported for ventilated slab systems are based on simplified thermal analysis and do not take account the multi-dimensional heat transfer associated with hollow cores with floor slabs. The research study outlined in the Ph.D. dissertation starts with the development of a comprehensive simulation environment to accurately assess the thermal performance of hollow core ventilated slab systems. Specifically, a transient three-dimensional numerical solution is developed and validated suitable for the thermal analysis of hollow core ventilated slab systems. The simulation environment is then used to perform a series of parametric analyses to evaluate the performance of ventilated slab systems under various design and operating conditions. In particular, the effects on energy efficiency performance of the ventilated slab systems are considered for a wide range of parameters including convective heat transfer inside hollow cores, supply air inlet temperatures, air mass flow rates, hollow core depths, and hollow core diameters. In order to reduce computational efforts, the use of two-dimensional numerical model instead of three-dimensional numerical solution is explored and verified to evaluate the thermal performance of ventilated slab systems effectively. In addition to sensible heat transfer analysis, moisture condensation within the hollow cores is investigated to evaluate the potential for water accumulation and mold growth risk. Two models, a heat and moisture room model and an enthalpy heat exchanger model, are implemented and validated. The enthalpy heat exchanger model in the simulation environment is capable of accurately predicting the variations of the humidity ratios of the supply air and the room ambient air. As part of the application of the developed simulation environment, optimum control strategies are developed for enhancing the performance of ventilated slab systems to heat and cool the commercial buildings. The optimum control strategy is identified using Genetic Algorithm optimization techniques. A comparative analysis of the energy performance of ventilated slab systems against conventional VAV systems for a typical office building is carried out under various climatic conditions. Based on the analysis, a set of design and operation guidelines for the hollow core ventilated slab systems is developed in order to enhance their energy performance for US commercial buildings.

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