Total heat recovery : heat and moisture recovery from ventilation air / Li-Zhi Zhang.

Format:

Book

Author/Creator:

Zhang, Li-Zhi.

Language:

English

Subjects (All):

Heat exchangers.

Ventilation.

Heat recovery.

Condensation.

Moisture.

Humidity--Control.

Humidity.

Water harvesting.

Buildings--Energy conservation.

Buildings.

Physical Description:

1 online resource (328 p.)

Edition:

1st ed.

Place of Publication:

New York : Nova Science Publishers, c2008.

Language Note:

English

Summary:

Energy has been described as "that which makes things go". Air conditioning accounts for 1/3 of the total energy use in society. Further, ventilation air accounts for 20-40% of the cooling load for HVAC (Heating, ventilating, and Air conditioning) industry. The ratio can be even higher in hot and humid regions where latent load from fresh air is as heavy as 50% of the cooling load. In this book, the systems and performances used for total heat recovery are introduced. They can be classified into two categories: energy wheels and stationary total heat exchangers. Energy wheels and membrane based total heat exchangers are specially described. Heat and mass transfer modelling of the system are performed. Influences of key material and design parameters on the system performance are discussed. Novel membranes including hydrophobic-hydrophilic composite membrane and composite supported liquid membrane are developed for total heat exchangers and are characterised. Sorption and diffusion of moisture in hygroscopic materials are the key parameters influencing latent heat recovery capability. Their appraisal methods are provided and implemented. Besides materials side intensification, air side intensification measures are taken as well. Plate-fin and cross corrugated triangular ducts are two important structures that are introduced. Plate-fin is compact and mechanically strong. Cross-corrugated triangular ducts are a new type of primary surface heat mass exchanger. The basic transport data in these structures are provided. Convective heat and mass transfer coefficients in plate-fin ducts of finite fin conductance with various cross sections are numerical obtained. Fluid flow and heat transfer in cross-corrugated triangular ducts are estimated by considering laminar, transitional, and turbulent complex flow regimes. Based on the fundamental heat mass transfer data, the book illustrates some examples of the applications of total heat recovery in novel HVAC systems. Chilled-ceiling combined with desiccant cooling and independent air dehumidification are two pioneering trends in air conditioning industry. They overcome the shortcomings of conventional all air systems by decoupling the treatment of sensible load with latent load. Partial or full total heat recovery are realised in combination with these novel systems, which contribute to reduced energy use with increased indoor humidity control, even in transit seasons when traditional air conditioning systems fail to control humidity. The component modelling of various key equipments like refrigeration cycle, heat pumps, regenerative wheels, heat exchangers, cooling coils, are conducted to estimate their energy performance and their effects on indoor thermal and humidity performance. The book combines theoretical analysis with engineering practices. It covers a wide range of knowledge from fundamental heat mass transfer data to novel systems design and performance analysis, from materials synthesis, characterisation to thermodynamics and fluid dynamics. As a kernel part, numerical heat mass transfer provides the tool for component modelling. The book provides crucial insight and design guidelines for the total heat recovery focused air conditioning industry.

Contents:

Intro

TOTAL HEAT RECOVERY: HEAT AND MOISTURE RECOVERYFROM VENTILATION AIR

NOTICE TO THE READER

CONTENTS

PREFACE

TOTAL HEAT RECOVERY IN AIR-CONDITIONING

ABSTRACT

1.1. INTRODUCTION

1.2. OPPORTUNITIES AND CHALLENGES

1.3. CONCLUSION

REFERENCES

ENERGY RECOVERY POTENTIALS

2.1. INTRODUCTION

2.2. ENERGY CALCULATIONS

2.3. CONCLUSION

ESTIMATION OF SORPTION AND DIFFUSION PROPERTIES OF HYGROSCOPIC MATERIALS

NOMENCLATURE

3.1. INTRODUCTION

3.2. SORPTION AND DIFFUSIVITY IN A THERMO-HYGROSTAT

Sorption Experiments

Drying Experiments

Calculation of Diffusivity

Uncertainty Analysis

Sorption Isotherms

Sorption Curves

Regeneration Curves

Moisture Diffusivity

3.3. FLUID FLOW AND MASS TRANSFER IN A NOVEL EMISSION CELL

Mathematical Models

Discretisation and Solution Strategy

Experimental Work

Local and Mean Sherwood Numbers

Flow Patterns

Humidity Profiles

3.4. MEASUREMENT OF MOISTURE DIFFUSIVITY WITH THE CELL

The Whole Set-up

Model Development

Estimation of Moisture Diffusivity

3.5. CONCLUSION

PERFORMANCE OF ENERGY WHEELS

4.1. INTRODUCTION

4.2. MATHEMATICAL MODEL

Performance Index

4.3. PERFORMANCE ANALYSIS

Temperature and Humidity Profiles

Effects of Rotary Speed

Effects of NTU

Psychrometric Cycle

4.4. CONCLUSION

HEAT MASS TRANSFER IN BENDED SINUSOIDAL NARROW DUCTS

5.1. INTRODUCTION

5.2. FLOW AND HEAT MASS TRANSFER MODEL

Basic Equations

5.3. BOUNDARY FITTED COORDINATES

Finite Difference Equations

5.4. FRICTION AND MASS TRANSFER COEFFICIENTS

Validation of the Procedure

Effects of Bending Ratios

5.5. CONCLUSION

REFERENCES.

CONVECTIVE HEAT MASS TRANSFER IN PLATE-FIN CHANNELS

6.1. INTRODUCTION

6.2. SINUSOIDAL DUCTS OF FINITE FIN CONDUCTANCE

Governing Equations

Numerical Method

RESULTS AND DISCUSSION

6.3. RECTANGULAR DUCT

Parallel-plates Channels

6.4. TRIANGULAR DUCT

6.5. CONVECTIVE MASS TRANSFER COEFFICIENTS

Boundary Conditions

6.6. COMPARISONS OF HEAT AND MASS TRANSFER

6.7. CONCLUSION

EFFECTIVENESS CORRELATIONS OF TOTAL HEAT EXCHANGERS

7.1. INTRODUCTION

7.2. EFFECTIVENESS-NTU CORRELATIONS

Deduction of Effectiveness Correlations

Validation

7.3. CORRELATIONS FOR PLATE-FIN TOTAL HEAT EXCHANGER

7.4. AN APPLICATION EXAMPLE

Problem

Solution

7.5. CONCLUSION

NUMERICAL SIMULATION OF TOTAL HEAT EXCHANGERS

8.1. INTRODUCTION

8.2. PARALLEL-PLATES EXCHANGER

Numerical Methods

Membrane Surface Values

Nusselt and Sherwood Numbers

8.3. PLATE-FIN EXCHANGER

Heat and Mass Transfer in Air Streams

Heat and Mass Transfer through Plates

Simulation Case

Solution Procedure

8.4. CONCLUSION

NOVEL MEMBRANES FOR TOTAL HEAT EXCHANGER

9.1. INTRODUCTION

9.2. HYDROPHOBIC-HYDROPHILIC COMPOSITE MEMBRANE

Membrane Preparation

Vapor Permeation Measurements

Characterization of the Membrane

Vapor Permeation Tests

SEM Studies

Contact Angles

Sorption Tests

9.3. COMPOSITE SUPPORTED LIQUID MEMBRANE

Preparation of the Supported Liquid Membranes

Moisture Transport Measurement

Analysis of Transfer Resistance

Moisture Transfer through the Composite Membrane

Gas Transport in Porous Media

Pore Size Distribution.

Mass Transfer of Vapor through a Single Membrane Pore

Poisseuille Flow

Knudsen Diffusion

Molecule Diffusion

Combined Flow

Total Mass Flux Across a Membrane

Effective Diffusivity in the First and the Third Layer

Effective Diffusivity in the Second Layer

Moisture Diffusion in the Air Gap

Moisture Permeability

Resistance Analysis

Effects of Protective Layers

Effects of Liquid Layer

9.4. HEAT CONDUCTIVITY OF MEMBRANES

Composite Supported Liquid Membrane

Composite Hydrophobic-hydrophilic Membrane

9.5. MEMBRANE SELECTIVITY

9.6. CONCLUSION

HEAT MASS TRANSFER IN CROSS-CORRUGATED TRIANGULAR DUCTS

10.1. INTRODUCTION

10.2. LAMINAR FLOW

Mathematical Model

Solution Method and Validation

Flow Distribution and Friction Factor

Temperature Distribution and Nusselt Number

10.3. TURBULENT FLOW

Turbulence Models

Standard k-ε Model

Renormalized k-ε model

Low Reynolds k-ω Model

Full Reynolds Stress Modeling

Solution Method

Model Validation

Turbulent Flow and Heat Transfer

10.4. TRANSITIONAL FLOW

Geometry

Transitional Flow and Heat Transfer

10.5. CONVECTIVE MASS TRANSFER

10.6. COMBINED WITH MEMBRANES

10.7. CONCLUSION

APPLICATIONS OF TOTAL HEAT RECOVERY

11.1. INTRODUCTION

11.2. DESICCANT WHEEL WITH CHILLED CEILING

Conventional all-Air System

Desiccant Cooling (DC) with Chilled-Ceiling

Pre-cooling Desiccant Cycle with Chilled-Ceiling

Component Modeling

Building Configurations

Operating Parameters in the Cycle

Annual Primary Energy Consumptions

Indoor Humidity

Capital Cost.

11.3. INDEPENDENT AIR DEHUMIDIFICATION

System Descriptions

Performance Analysis

Annual Primary Energy Requirements

11.4. CONCLUSION

INDEX.

Notes:

Description based upon print version of record.

Includes bibliographical references and index.

ISBN:

1-60876-275-0

OCLC:

433975993