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...and the radiative/convective split as input data. This paper addresses the need to experimentally determine the lighting heat gain parameters for a range of common luminaires under realistic operating conditions. The paper presents both the measurement procedures and the computational procedures required to obtain derived results. The paper also discusses the uncertainty analysis and the accuracy of experimental results and compares different techniques that can be used to obtain the lighting heat gain parameters. Estimated uncertainties in the conditioned space, the ceiling plenum, and the convective fractions are relatively high. These uncertainties vary between [+ or -]0.06 and [+ or -]0.19. Estimated uncertainties in the shortwave and the longwave radiative fractions are relatively low, varying between [+ or -]0.01 and [+ or -]0.08 but mostly less than [+ or -]0.03. A companion paper presents experimental results along with their estimated uncertainties, discusses the effects of various parameters on the measured results, and provides guidelines for the application of the experimental results.

INTRODUCTION

The heat gain due to lights constitutes a significant contribution to the hourly cooling load in many commercial buildings. Although all of the electrical power input to the lighting system is eventually converted to heat, the transport of lighting energy is very complex, particularly for a recessed luminaire, involving all three heat transfer mechanisms--radiation, convection, and conduction--to two spaces, the conditioned space and the ceiling plenum. Figure 1 illustrates the transport of lighting energy for various luminaires typically used in commercial buildings. The distribution of lighting energy is dependent on numerous variables, including the type of luminaire and lamp, the building construction, the room airflow configuration, and the setpoints of the conditioned space.

In order to account for the heat gain due to lights, both of ASHRAE's new cooling load calculation procedures (Pedersen et al. 1998) use a simple lighting heat gain model. The model requires two lighting heat gain parameters--the conditioned space/ceiling plenum split and the radiative/convective split (Spitler et al. 1997). The conditioned space/ceiling plenum split is the fraction of the lighting power converted to the lighting heat gain of the conditioned space and the fraction of the lighting power converted to the ceiling plenum's lighting heat gain. These fractions are only required for in-ceiling (or recessed) luminaires since it can be assumed that the heat generated by all other luminaires is entirely dissipated in the conditioned space. On the other hand, the radiative/convective split is the fraction of the lighting heat gain of the conditioned space that is transferred as radiation and the fraction that is transferred as convection. These fractions are required for both in-ceiling and non-in-ceiling luminaires. In the heat balance (HB) method, the radiative component of the conditioned space lighting heat gain participates in the inside surface heat balance with some prescribed radiative distribution, while the convective component is assumed to go immediately to the air heat balance (i.e., instantaneously becomes cooling load). The HB method treats shortwave and longwave radiation due to lights separately, meaning that shortwave radiation due to lights can be lost from the space through transparent surfaces. The radiant time series (RTS) method, on the other hand, does not distinguish shortwave and longwave radiation. The RTS method uses the so-called nonsolar radiant time factors to convert the radiative component of the conditioned space lighting heat gain into cooling load. Like the HB method, the convective component is assumed to become cooling load immediately.

[FIGURE 1 OMITTED]

Published lighting heat gain parameters in the 2005 ASHRAE Handbook--Fundamentals (ASHRAE 2005) do not present the conditioned space/ceiling plenum "heat gain" split. In addition, the 2005 Handbook data may be obsolete due to recent advancements in lighting technologies. The current research addresses the need to provide relevant lighting heat gain parameters for a range of common luminaires. The lighting heat gain parameters can be economically determined by detailed lighting models (Chung and Loveday 1998a, 1998b; Sowell and O'Brien 1973; Sowell 1990, 1993; Walton 1993). However, these lighting models have only been validated for one type of luminaire considered in the current study, namely, the recessed luminaire with acrylic lens. In addition, the lighting models require appropriate correlations of convection coefficients in order to predict accurate results (Chung and Loveday 1998a, 1998b; Sowell and O'Brien 1973; Sowell 1990, 1993; Walton 1993). Unfortunately, such correlations are not currently available for most luminaires. Therefore, experimental methods are preferable to numerical methods for the current study.

Although similar lighting and thermal performance parameters can be accurately measured using the small-scale calorimeter measurement method (IESNA 2000), the thermal conditions of the calorimeter do not necessarily reflect those of a realistic building environment, particularly the airflow field within the lamp chamber and around the luminaire. The primary objective of this study is, therefore, to accurately measure the lighting heat gain parameters under realistic operating conditions in a full-scale experimental room. An additional objective of the current study is to provide the experimental results in a format that can be readily applied to the ASHRAE cooling load procedures.

This paper presents an experimental method to determine the lighting heat gain parameters required for cooling load calculations. A companion paper (Chantrasrisalai and Fisher 2007) shows experimental results along with estimated uncertainties, discusses the effects of various parameters on the lighting heat gain parameters, and provides guidelines for the application of the experimental results. Previous studies related to the cooling load effect of lights are discussed in the next section. Following the literature review, the experimental method and the facility and instrumentation are described. Next, the detailed experimental procedures and calculations required to obtain the lighting heat gain parameters are presented. Finally, validation of the experimental method is discussed.

LITERATURE REVIEW

In the past, extensive studies (Ball 1983a, 1983b; Chung and Loveday 1998a, 1998b; Kimura and Stephenson 1968; Mitalas and Kimura 1971; Mitalas 1973a, 1973b; Nevins et al. 1971; Nottage and Park 1969; Rundquist 1990; Sowell and O'Brien 1973; Sowell 1990, 1993; Treado and Bean 1990, 1992) have theoretically and experimentally attempted to analyze and quantify the effect of lights on the cooling load. Among these studies, the work done by Mitalas and Kimura (Mitalas and Kimura 1971; Mitalas 1973a, 1973b) and Treado and Bean (1990, 1992) are of particular interest since they are experimental studies using full-scale test rooms and are therefore directly applicable to the current research. Mitalas and Kimura (1971) used a room-sized calorimeter to determine the cooling load caused by lights. Based on experimental results measured in the calorimeter, Mitalas (1973a, 1973b) later presented design data to estimate the cooling load caused by lights. The design data included room transfer function coefficients (or weighting factors) and the conditioned space/ceiling plenum split. Mitalas's conditioned space/ceiling plenum split is a "cooling load" split, which is different from the "heat gain" split proposed in the current research. Treado and Bean (1990, 1992) describe an experimental study of the interaction between lighting and HVAC systems. They discuss a full-scale test facility similar to Mitalas's calorimeter. They show various lighting and thermal performance parameters, including lighting power consumption, light output, luminous efficacy, cooling load, air temperatures, minimum lamp wall temperature, as well as room transfer function coefficients. However, they provide no information regarding the lighting heat gain parameters. As previously discussed, Mitalas's conditioned space/ceiling plenum split is the cooling load split and, thus, is not applicable to the HB and RTS load calculation methods. The "Validation of Experimental Results" section of this paper compares the proposed conditioned space/ceiling plenum heat gain split with Mitalas's conditioned space/ceiling plenum cooling load split and discusses differences in the two parameters.

OVERVIEW OF TECHNICAL APPROACH

The experimental method required for the present research is based on two distinct experimental techniques: one for the conditioned space/ceiling plenum split and one for the radiative/convective split. The experimental technique for the conditioned space/ceiling plenum split is used for in-ceiling (or recessed) luminaires but is not required for non-in-ceiling luminaires since it is assumed that the heat generated by pendant or ceiling-mounted luminaires is all dissipated in the conditioned space. On the other hand, the experimental technique for the radiative/convective split is used for both types of luminaires. The following sections give an overview of technical approaches used in determining the conditioned space/ceiling plenum split and the radiative/convective split.

The Conditioned Space/Ceiling Plenum Split

The technical approach for estimating the conditioned space/ceiling plenum split is based on the application of the air heat balance to a well-defined control volume. The basic formulation, shown in Equation 1, assumes steady-state, steady-flow conditions and requires measurement of the volumetric flow rate through...

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