A nodal model has been developed to represent room heat transfer in displacement ventilation and chilled ceiling systems. The model uses precalculated air flow rates to predict the air temperature distribution and the division of the cooling load between the ventilation air and the chilled ceiling. The air movements in the plumes and the rest of the room are represented separately using a network of ten air nodes. The values of the capacity rate parameters are calculated by solving the heat and mass balance equations for each node using measured temperatures as inputs. Correlations between parameter values for a range of cooling loads and supply air flow rates are presented.

VL - 36 UR - http://www.ibpsa.org/proceedings/BS1999/BS99_D-05.pdf IS - 6 ER - TY - JOUR T1 - Numerical Investigation of Transient Buoyant Flow in a Room with a Displacement Ventilation and Chilled Ceiling System JF - International Journal of Heat and Mass Transfer Y1 - 2001 A1 - Simon J. Rees A1 - James J. McGuirk A1 - Philip Haves AB -The air flow in the office ventilation system known as displacement ventilation is dominated by a gravity current from the inlet and buoyant plumes above internal heat sources. Calculations of the flow and heat transfer in a typical office room have been made for this type of ventilation system used in conjunction with chilled ceiling panels. These calculations have been made in parallel with full size test chamber experiments. It has been found that with higher values of internal load (45 and 72 W m^{−2} of floor area) the flow becomes quasi-periodic in nature. Complex lateral oscillations are seen in the plumes above the heat sources which impinge on the ceiling and induce significant recirculating flows in the room. The frequency spectra of the transient calculations show good agreement with those of the experimental results. Comparison is also made between calculated mean room air speeds and temperature profiles and measured values.

A qualitative comparison is presented between three current North American and U.K. design cooling load calculation methods. The methods compared are the ASHRAE Heat Balance Method, the Radiant Time Series Method and the Admittance Method, used in the U.K. The methods are compared and contrasted in terms of their overall structure. In order to generate the values of the 24 hourly cooling loads, comparison was also made in terms of the processing of the input data and the solution of the equations required. Specific comparisons are made between the approximations used by the three calculation methods to model some of the principal heat transfer mechanisms. Conclusions are drawn regarding the ability of the simplified methods to correctly predict peak-cooling loads compared to the Heat Balance Method predictions. Comment is also made on the potential for developing similar approaches to cooling load calculation in the U.K. and North America in the future.

VL - 6 IS - 1 ER - TY - Generic T1 - A Nodal Model for Displacement Ventilation and Chilled Ceiling Systems in Office Spaces T2 - Building Simulation ’99 Y1 - 1999 A1 - Simon J. Rees A1 - Philip Haves AB -A nodal model has been developed to represent room heat transfer in displacement ventilation and chilled ceiling systems. The model uses precalculated air flow rates to predict the air temperature distribution and the division of the cooling load between the ventilation air and the chilled ceiling. The air movements in the plumes and the rest of the room are rep- resented separately using a network of ten air nodes. The values of the capacity rate parameters are calculated by solving the heat and mass balance equations for each node using measured temperatures as inputs. Correlations between parameter values for a range of cooling loads and supply air flow rates are presented.

JF - Building Simulation ’99 CY - Kyoto, Japan UR - http://www.ibpsa.org/proceedings/BS1999/BS99_D-05.pdf ER - TY - JOUR T1 - Comparison of North American and U.K. Cooling Load Calculation Procedures - Methodology JF - ASHRAE Transactions Y1 - 1998 A1 - Jeffrey D. Spitler A1 - Simon J. Rees A1 - Philip Haves AB - This paper describes the methodology used in a quanti- tative comparison between the current North American and United Kingdom cooling load calculation methods. Three calculation methods have been tested as part of a joint ASHRAE/CIBSE research project: the ASHRAE heat balance method and radiant time series method and the admittance method, used in the U.K. A companion paper (Rees et al.1998) describes the results of the study. The quantitative comparison is primarily organized as a parametric study—each building zone/weather day combination compared may be thought of as a combination of various parameters, e.g., exterior wall type, roof type, glazing area, etc. Specifically, this paper describes the overall organization of the study, the parameters and parameter levels that can be varied, and the tools developed to create input files, automate the load calculations, and extract the results. A brief descrip- tion of the cooling load calculation procedure implementa- tions is also given. The methodology presented and the tools described could also be used to make comparisons between other calculation methods. VL - 104 IS - 2 ER - TY - JOUR T1 - Comparison of North American and U.K. Cooling Load Calculation Procedures - Results JF - ASHRAE Transactions Y1 - 1998 A1 - Simon J. Rees A1 - Jeffrey D. Spitler A1 - Philip Haves AB - Calculation of design cooling loads is of critical concern to designers of HVAC systems. The work reported here has been carried out under a joint ASHRAE/CIBSE research project to compare design cooling calculation methods. Three calculation methods have been tested, the ASHRAE heat balance method and radiant time series method, and the admit- tance method, used in the U.K. The results presented in this paper show the general trends in over/underprediction of peak load in the simplified methods compared to the heat balance method. The performance of the simplified methods is explained in terms of some of the underlying assumptions in the methods and by reference to specific examples. VL - 104 IS - 2 ER - TY - Generic T1 - A Model of a Displacement Ventilation/Chilled Ceiling Cooling System Suitable for Annual Energy Simulation T2 - Building Simulation '95 Y1 - 1995 A1 - Simon J. Rees A1 - Philip Haves JF - Building Simulation '95 CY - Madison, WI ER - TY - Generic T1 - Modelling and Simulation of Low Energy Cooling Systems T2 - Tsinghua HVAC-95 Y1 - 1995 A1 - Philip Haves A1 - Simon J. Rees A1 - Harrington, L. JF - Tsinghua HVAC-95 CY - Bejing, China ER -