Energy-Optimal Structures of HVAC System for Cleanrooms as a Function of Key Constant Parameters and External Climate

Mieczysław Porowski,Monika Jakubiak

doi:10.3390/en15010313

Abstract

This article presents approximating relations defining energy-optimal structures of the HVAC (Heating, Ventilation, Air Conditioning) system for cleanrooms as a function of key constant parameters and energy-optimal control algorithms for various options of heat recovery and external climates. The annual unit primary energy demand of the HVAC system for thermodynamic air treatment was adopted as the objective function. Research was performed for wide representative variability ranges of key constant parameters: cleanliness class—Cs (ISO5÷ISO8), unit cooling loads—q˙j (100 ÷ 500) W/m2 and percentage of outdoor air—αo (5 ÷ 100)%. HVAC systems are described with vectors x¯ with coordinates defined by constant parameters and decision variables, and the results are presented in the form of approximating functions illustrating zones of energy-optimal structures of the HVAC system x¯* = f (Cs, q˙j, αo). In the optimization procedure, the type of heat recovery as an element of optimal structures of the HVAC system and algorithms of energy-optimal control were defined based on an objective function and simulation models. It was proven that using heat recovery is profitable only for HVAC systems without recirculation and with internal recirculation (savings of 5 ÷ 66%, depending on the type of heat recovery and the climate), while it is not profitable (or generates losses) for HVAC systems with external recirculation or external and internal recirculation at the same time.

Highlights

HVAC systems for cleanrooms generate very high energy consumption for thermodynamic treatment and forcing through air
The aim of the presented paper is to calculate approximating functions describing optimal structures of the HVAC system for cleanrooms depending on key constant parameters: cleanliness class (Cs), percentage of outdoor air and unit cooling load and determination of the energy-optimal control algorithms for heat recovery options and the outdoor climate
This article presents the original results of research on the optimization of HVAC systems for cleanrooms

Summary

Introduction

HVAC systems for cleanrooms generate very high energy consumption for thermodynamic treatment and forcing through air. The aim of the presented paper is to calculate approximating functions describing optimal structures of the HVAC system for cleanrooms depending on key constant parameters (arguments): cleanliness class (Cs), percentage of outdoor air (αo) and unit cooling load (qj) and determination of the energy-optimal control algorithms for heat recovery options and the outdoor climate. After determining the X matrix, in the step of the optimization procedure, the real required ranges for the variability of key fixed parameters in cleanroom applications, are determined: cleanliness class (Csk), share of outside air (αok) and unit cooling load (qjk) On this basis, a representative set of combinations of the values of the key parameters of the HVAC system constants is determined, and for each of these combinations, the optimal structure of the HVAC system xn∗gk is determined based on an algorithm from the set of permissible structures (X matrices). Determination of the energy-optimal variant of the HVAC system—vector x∗, taking into account the optimal structure and the optimal type of heat recovery

Acceptable Structures of HVAC System

Optimal Structure Selection Algorithm

Approximating Functions

Validation of the Calculation Results

Findings

Conclusions