Air Temperature Stratification Research Articles

Enhancing crop yield in hydroponic greenhouses: Integrating latent heat storage and forced ventilation systems for improved thermal stratification

Greenhouses play a crucial role in modern agriculture, creating an ideal environment for plant growth. Nevertheless, maintaining air temperature distribution inside a greenhouse remains a significant challenge due to the inherent tendency of warm air to stratify. This paper proposes an innovative integrated system that combines both heating and ventilation mechanisms. Its primary objective is to tackle the issue of air temperature stratification inside greenhouses, ultimately enhancing the microclimate to optimize crop production. The heating system comprises of a solar air heater with latent heat storage energy and a ventilation system designed to promote air circulation while eliminating stagnant zones. An experimental study was conducted to assess the performance of the integrated heating and ventilation systems in various greenhouse scenarios. The study begins by examining the thermal performance of the solar collector and its subsequent impact on the indoor environment of the hydroponic greenhouse. The results showed that the solar collector has a remarkable thermal performance with a daily energy efficiency between 32 % and 44 %. Incorporating the heating system into the greenhouse led to significant improvements in temperature stability, particularly during nighttime hours, when temperatures ranged from 17 °C to 20 °C. This translated to a temperature increase of 2 °C to 6 °C compared to greenhouses without heating, effectively illustrating the benefits of incorporating phase change materials into the heating system. The combination the heating and ventilation systems, resulted in a reduction of over 3 °C in the temperature difference between actual and desired levels.

Stratification Breakdown in Antarctic Coastal Polynyas. Part I: Influence of Physical Factors on the Destratification Time Scale

Abstract This study examines the process of water-column stratification breakdown in Antarctic coastal polynyas adjacent to an ice shelf with a cavity underneath. This first part of a two-part sequence seeks to quantify the influence of offshore katabatic winds, alongshore winds, air temperature, and initial ambient stratification on the time scales of polynya destratification through combining process-oriented numerical simulations and analytical scaling. In particular, the often-neglected influence of wind-driven circulation on the lateral transport of the water formed at the polynya surface—which we call Polynya Source Water (PSW)—is systematically examined here. First, an ice shelf–sea ice–ocean coupled numerical model is adapted to simulate the process of PSW formation in polynyas of various configurations. The simulations highlight that (i) before reaching the bottom, majority of the PSW is actually carried away from the polynya by katabatic wind–induced offshore outflow, diminishing water-column mixing in the polynya and intrusion of the PSW into the neighboring ice shelf cavity, and (ii) alongshore coastal easterly winds, through inducing onshore Ekman transport, reduce offshore loss of the PSW and enhance polynya mixing and PSW intrusion into the cavity. Second, an analytical scaling of the destratification time scale is derived based on fundamental physical principles to quantitatively synthesize the influence of the physical factors, which is then verified by independent numerical sensitivity simulations. This work provides insights into the mechanisms that drive temporal and cross-polynya variations in stratification and PSW formation in Antarctic coastal polynyas, and establishes a framework for studying differences among the polynyas in the ocean.

An Aisle Displacement Ventilation System for Twin-Aisle Commercial Airliner Cabin

The environmental control system in most commercial airliner cabins supplies air from shoulder and ceiling level and exhausts air at floor level on both sides of the cabin walls. The ventilation system mixes air in the cabins to create a relative uniform air temperature distribution which is great for passengers’ thermal comfort. However, the mixing ventilation also enhances airborne contaminant transfer. Many displacement ventilation methods have been proposed to use in aircraft cabins, but the disadvantages of the ventilation approach are usually creating draft on the passengers’ ankles and high air temperature stratification between passengers’ heads and feet. This investigation developed an aisle displacement ventilation (ADV) system which can reduce air temperature stratification effectively without occupying the legroom space under the seats, so it is good for passengers and crew members’ comfort and friendly for luggage storage, in addition, it can also be easily installed in aircraft cabins. By installing the system in a five-row, twin-aisle cabin mockup, our study found that the ADV system can create a low air velocity distribution in the cabin and can maintain an acceptable air temperature stratification without draft. The system created an uprising airflow which can effectively remove airborne contaminant which was generated from index passengers’ respiratory activities. The experimental data were used to validate a computational-fluid-dynamics (CFD) program. The validated CFD program was used to compare the ADV with under-seat displacement ventilation (USDV) and underfloor air distribution (UFAD) system along the aisles. The comparison results show that the ADV had obvious better thermal comfort than the other two systems, and the cabin air quality of the three ventilation systems was similar, all far better than the “perfectly-mixed” ventilated condition.

An experimental comparison of radiant wall and ceiling cooling system integrated with ground source heat pump and direct expansion fan coil system in a highly glazed office room

Hydronic radiant systems, which provide a thermal comfort environment, come to the fore in different building applications due to their energy saving potential and being integrated with renewable energy systems. The aim of this study is to present a full-scale experiment to compare the thermal comfort performances of radiant ceiling, wall and wall + ceiling systems coupled ground source heat pump and direct expansion fan coil system implemented in Yildiz Technical University Science and Technology Application and Research Center, Istanbul, Turkey. Air velocity, horizontal and vertical air temperature differences, mean radiant temperature and humidity values, which are four physical parameters that can affect the thermal satisfaction of office workers for 9 different experimental conditions, are measured for fan coil and all radiant systems. The results indicate that vertical temperature differences between ankle and head level vary from 0.9 °C to 1.4 °C for both fan coil system and all radiant system configurations in different location of the test room. Acceptable overall comfort in indoor environments Class A only showed stable performance with an average of 0.12 PMV and 5.3 % PPD when ceiling + wall radiant panels were actively cooled. The result shows that the difference between room air temperature and room operating temperature varies between 0.45 °C and 0.6 °C when cooling loads are met by radiant systems. This may not make it possible to use indoor air temperature instead of indoor operating temperature in the control of radiant systems. Moreover, the thermal environment of the radiant system are more uniform than fan coil system due to low air temperature stratification, air velocity and small differences between mean radiant temperature and indoor air temperature.

An aisle displacement ventilation system for twin-aisle commercial airliner cabin

The environmental control system in most commercial airliner cabins supplies air from shoulder and ceiling level and exhausts air at floor level on both sides of walls. The ventilation system mixes air in the cabins to create a uniform air temperature distribution that is great for thermal comfort. However, the mixing ventilation also enhances airborne contaminant transfer. Displacement ventilation has been proposed for use in cabins, but they may create high air temperature stratification and draft. This investigation developed an aisle displacement ventilation (ADV) system that can reduce air temperature stratification and be easily installed in cabins. By installing the system in a five-row, twin-aisle cabin mockup, our study found that ADV can create a low air velocity distribution in the cabin and can maintain an acceptable air temperature stratification without draft. The system created an uprising flow that can effectively remove airborne contaminant generated from respiratory activities. The experimental data were used to validate a computational-fluid-dynamics (CFD) program. The validated CFD program was used to compare the ADV with the under-seat displacement ventilation (USDV) and the underfloor air distribution (UFAD) along the aisles. The ADV had better thermal comfort than the other two systems, but the cabin air quality of the three ventilation systems was similar.

Experimental study on energy consumption and thermal environment of radiant ceiling heating system for different types of rooms

This paper investigates energy consumption and thermal environment performance of a radiant ceiling heating system serving different types of rooms in the same building. Four types of rooms with different functions, namely restaurant, office, flight control room, and conference room, were chosen in this study. Energy consumption and thermal environment parameters were measured in different rooms, including the heating energy consumption intensity, indoor air temperature, surface temperature of the building envelope, air temperature stratification, and vertical temperature gradient. The results show that the heating energy consumption intensity is about 19.63 W/m2, which is about 30% lower than the heating index recommended in the regional standard. The heating indexes per unit area of the restaurant, office, flight control room, and conference room are 33.41, 17.36, 18.91, and 20.32 W/m2, respectively. The unit volume heating energy consumption of the flight control room, which is a large space, is significantly lower than that of the office, which is a small space. Moreover, there are also differences regarding the indoor thermal environment of the different types of rooms. Factors such as solar radiation, outdoor cold air infiltration, and indoor occupancy rate are the main factors that influence the indoor thermal environment. In general, the energy consumption level of radiant ceiling heating systems for larger spaces is lower, and the indoor thermal environment is better. Therefore, radiant ceiling heating systems are more suitable for larger rooms.

Air temperature stratification when flowing between rooms

The article presents the regularities of the vertical change in the air temperature of a ventilated room for various purposes, where the excess of sensible heat dominates, in the first case, when there is no process of air flow through the opening in a common vertical fence between the rooms located in a row, or the second case, when a similar air flow is observed. In heat-stressed rooms, the general ventilation arrangement scheme provides for the removal of air from the upper volume of the room. To determine the required air exchange with point, two-zone or multi-zone mathematical models of a ventilated room, it is necessary to have a reliable apparatus for determining the gradient of the vertical air parameters change for a ventilated room. The reasonably determined value of the gradient of the air temperature change along the vertical of the ventilated room makes it possible to calculate the air flow between different volumes inside the ventilated room. Determination of the air temperature near the suction flare makes it possible to determine the required air exchange more reasonably. A method is given for calculating the distribution of air temperature in rooms with an excess of apparent heat over the height of the room in the first case, when there is no process of air flow through the opening in the common vertical fence between the rooms located in a row, or the second case, when a similar air flow is observed. This takes into account the height of the supply air distributors relative to the working (serviced) area. Reasonable determination of the air temperature at different points in the room with an excess of sensible heat allows a correct calculation of the required air exchange. The presented method for determining the gradient of air temperature stratification along the height of the room with air flow between adjacent rooms and without it contributes to the reasonable determination of the air temperature at the suction flame of the exhaust air distributor, which increases the reliability of calculating the required air exchange.

Experimental Study on Thermal Response Characteristics of Indoor Environment with Modular Radiant Cooling System

The radiant cooling system has a substantial energy-saving effect and can be widely applied in different kinds of low-energy buildings. This article reports the experimental study of the design strategy of the radiant cooling system in low-energy buildings from the perspective of thermal response characteristics of an indoor environment. Two types of a modular radiant cooling system, namely, the copper tube radiant cooling (CTRC) and the capillary radiant cooling (CRC) systems, were investigated. The experiments were conducted in two office rooms characterized by low energy consumption. In total, 16 cases (eight for CTRC and eight for CRC) were analyzed, covering supply water temperature with a range of 12–19 °C. The experimental results show that the supply water temperature has a more substantial effect on the temperature distribution of the envelope for CTRC, than that of CRC. The indoor air temperature stratification is acceptable in the active area of the occupant with a modular radiant cooling system. Moreover, the thermal response of the envelope is highly sensitive to the lower supply water temperature (below 16 °C) using CTRC and to the higher supply water temperature (above 15 °C) using CRC. The low supply water temperature (below 15 °C) can improve the thermal stability speed of indoor air to a greater degree using CTRC, than that of CRC. The supply water temperature for CTRC with 15–16 °C, and 18–19 °C for CRC in low-energy buildings can exert an optimal cooling benefit.

Dynamic performance of displacement ventilation in a lecture hall

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design since it directly relates to thecalculation of the required supply airflow rate. Inaccurate temperature prediction can cause poor thermal comfort and wrong sizing of the ventilation and cooling systems. A heat balance-based method is usually applied in displacement ventilation (DV) design when overheating is the primary indoor climate concern. The temperature gradient in DV systems is usually calculated with lumped-parameter nodal models. Several simplified nodal models were developed and implemented in the various building simulation software to estimate the temperature stratification in rooms with DV. Recent studies reveal that the multi-nodal models provide the most accurate temperature gradient prediction. However, the majority of dynamic calculation methods assumes either complete mixing of zone air or linearised temperature gradient. The present study introduces the dynamic temperature gradient model for DV and investigates the effect of thermal mass on the temperature stratification. The model was validated with the experimental results of a lecture room with displacement ventilation. The room air temperature measurements were conducted during three weeks at 20 different heights. The supply air temperature and occupancy rate were recorded during each scheduled lecture. The developed dynamic nodal model is able to calculate the air temperatures in the occupied zone accurately. The effect of the thermal mass and changing heat gains on the room air temperature stratification is analysed for the lecture room with DV.

Dynamic design model of displacement ventilation

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design, since it directly relates to the calculation of the required supply air flow rate. Inaccurate temperature prediction can cause the poor thermal comfort and w sizing of the ventilation and cooling systems. Several simplified nodal models were developed and implemented in the various building simulation software to estimate the temperature stratification in rooms with DV. Recent studies reveal that the multi-nodal models provide the most accurate temperature gradient prediction. However, the most building simulation software uses the air models with only one air node. The present study introduces the dynamic temperature gradient model for DV and investigates the effect of thermal mass on the temperature stratification. The model was validated with the experimental results of the lecture room with displacement ventilation. The room air temperature measurements were conducted during three weeks at 20 different heights. The supply air temperature and occupancy rate were recorded during each scheduled lecture. The developed dynamic nodal model is able to accurately calculate the air temperatures in occupied zone. The effect of the thermal mass and varied heat loads on the indoor air temperature stratification is analysed for the lecture room with DV.

Validation of a transient zonal model to predict the detailed indoor thermal environment: Case of electric radiators and wood stoves

In building performance simulation (BPS), zonal models are intermediate models between standard models assuming perfectly-mixed room air and Computational Fluid Dynamics (CFD): they aim to predict the air temperature and velocity fields as well as the pollutant distribution inside a room using a computational time significantly lower than using CFD. The article aims at validating a transient zonal model that is currently implemented in the commercial BPS tool, IDA ICE. In theory, this one-dimensional model can address a large variety of airflows and requires almost no a priori knowledge of the flow to be computed. The model is validated against measurements in a laboratory heated by either electric radiators or an electric stove designed to mimic surface temperatures of real stoves. Unlike radiators, the case of stoves has never been addressed in the literature and is challenging due to the strong thermal coupling between the room air and walls. Heat emitters have been placed either in the middle of the room or along walls. The zonal model remarkably well predicts the time evolution of the air temperature stratification in the room for all test cases. For a heat emitter in a central position, the wall surface temperatures are predicted correctly. Nevertheless, for a heat emitter along walls, these walls cannot be considered isothermal anymore, an assumption found in most BPS tools. The paper suggests that an automatized method to divide walls in the vicinity of heat emitters is necessary for a reliable prediction of the wall surface temperatures.

Equivalent room air temperature based cooling load estimation method for stratum ventilation and displacement ventilation

Cooling load estimation is the base for the design and control of the air conditioning system. The indoor air temperature stratification of stratum ventilation and displacement ventilation contributes to the energy saving, but challenges the cooling load estimation. The existing building simulation tools are generally equipped with only the fully mixed air model and ignore the indoor air temperature stratification. This study proposes an equivalent room air temperature based cooling load estimation method to enable the fully mixed air model to accurately estimate the cooling load of stratum ventilation and displacement ventilation. The equivalent room air temperature is the air temperature with which the fully mixed air model can produce the same cooling load as that of stratum ventilation/displacement ventilation. The equivalent room air temperature is modelled as a function of the supply air temperature, supply airflow rate and room air temperature of stratum ventilation/displacement ventilation using response surface methodology. Case studies using the experimentally validated multi-node models are conducted to demonstrate the effectiveness of the proposed method. The mean absolute errors in the cooling load estimation by the proposed method for the constant-air-volume system and the variable-air-volume system are 0.02% and 5.78% respectively under stratum ventilation, and 0.07% and 4.78% respectively under displacement ventilation. Compared with the conventional method, the proposed method improves the accuracy in the cooling load estimation by 70.92%–99.94%.

Experimentally-determined characteristics of radiant systems for office buildings

Radiant heating and cooling systems have significant energy-saving potential and are gaining popularity in commercial buildings. The main aim of the experimental study reported here was to characterize the behavior of radiant cooling systems in a typical office environment, including the effect of ceiling fans on stratification, the variation in comfort conditions from perimeter to core, control on operative temperature vs. air temperature and the effect of carpet on cooling capacity. The goal was to limit both the first cost and the perceived risk associated with such systems. Two types of radiant systems, the radiant ceiling panel (RCP) system and the radiant slab (RS) system, were investigated. The experiments were carried out in one of the test cells that constitute the FLEXLAB test facility at the Lawrence Berkeley National Laboratory in March and April 2016. In total, ten test cases (five for RCP and five for RS) were performed, covering a range of operational conditions. In cooling mode, the air temperature stratification is relatively small in the RCP, with a maximum value of 1.6 K. The observed stratification effect was significantly greater in the RS, twice as much as that in the RCP. The maximum increase in dry bulb temperature in the perimeter zone due to solar radiation was 1.2 K for RCP and 0.9 K for RS – too small to have a significant impact on thermal comfort. The use of ceiling fans was able to reduce any excess stratification and provide better indoor comfort, if required. The use of thin carpet requires a 1 K lower supply chilled water temperature to compensate for the added thermal resistance, somewhat reducing the opportunities for water-side free cooling and increasing the risk of condensation. In both systems, the difference between the room operative temperature and the room air temperature is small when the cooling loads are met by the radiant systems. This makes it possible to use the air temperature to control the radiant systems in lieu of the operative temperature, reducing both first cost and maintenance costs.

A case study in performance measurements for the retrofitting of a library

An investigation of building performance through a comfort and operational quality standpoint is not too often discussed for Net-Zero Energy Buildings (NZEB). It would seem important that predications and claims for reducing energy-use in buildings and the move towards NZEB does not compromise comfort in buildings. A high school in Essendon, Victoria (near Melbourne) Australia undertook a retrofitting process to improve its existing library from a functional as well as an environmental standpoint. In the process, several pre- and post-measurements were made of building performance. An advanced packaged unit mechanical system applies a demand control ventilation system with a specialised control that promises uniform air temperature throughout the volume of the conditioned space. This system utilises staged compressors with variable speed drive fans and results in minimal background noise.For the mechanical system to deliver as promised, the building envelope was air pressure sealed to an international standard and double glazed (from single glass) and zoned according to orientation and spatial function. Efficient LED lighting was also applied to a dimming control responsive to occupancy and daylight. This level of building improvement requires before and after measurement procedures to assure and prove a quality performance for a near NZEB.Various measurements of pressurisation, air exchange rates through tracer gas, air temperature stratification, IAQ, as well as a continuous and localised comfort survey measurement all contribute to a pre and post assessment of building performance. This paper discusses several measurement processes considered useful to characterize the performance of an HVAC system in a retrofitted library space. As a result of the building envelope quality, subsequent monitoring of the mechanical conditioning system showed that it could have been reduced to half its specified size. Furthermore, sub-metering of the space indicates that the attention given to the lighting and conditioning systems has reduced their impact, so that plug loads are beginning to dominate and require attention if net zero energy building is to be targeted.

Investigation into air distribution systems and thermal environment control in chilled food processing facilities

Air flow distribution in chilled food facilities plays a critical role not only in maintaining the required food products temperature but also because of its impact on the facility energy consumption and CO2 emissions. This paper presents an investigation of the thermal environment in existing food manufacturing facilities, with different air distribution systems including supply/return diffusers and fabric ducts, by means of both in-situ measurements and 3D CFD simulations.Measurements and CFD simulations showed that the fabric duct provides a better environment in the processing area in terms of even and low air flow if compared to that with the diffusers. Moreover, temperature stratification was identified as a key factor to be improved to reduce the energy use for the space cooling. Further modelling proved that air temperature stratification improves by relocating the fabric ducts at a medium level. This resulted in a temperature gradient increase up to 4.1 °C in the unoccupied zone.

Flow dynamics in vadose zones with and without vegetation in an arid region

Flow dynamics in a thick vadose zone in an arid region, China was investigated using a field experiment at plots with bare soils and vegetated soils. Detailed pressure head profile along a depth of 8m, groundwater level, soil moisture content at surface, air temperature, and precipitation were observed over one year's time span. The temporal and spatial variations of pressure heads and hydraulic gradients over the time span elucidate the role of air temperature, precipitation, and soil stratification, the growth of vegetation, on the flow dynamics in the vadose zone. The dynamics includes freezing and thawing of surface soils, infiltration, evapotranspiration, distribution of moisture, and groundwater recharge. Estimated hydraulic gradients based on the observed pressure heads suggest that vegetation affected flow dynamics even at 3m below land surface during its growth seasons. The pressure head distributions at the vadose zone over the time span were found correlated well with soil stratification or heterogeneity. Afterward, we estimated the land-atmosphere interface flux, water uptake rate by the plants, and we then discussed the relationship between seasonal variation of temperature, precipitation, evaporation, plant growth, soil stratification (heterogeneity) and the flow dynamics in the vadose zone of the region.

An experimental study on the indoor thermal environment in prefabricated houses in the subtropics

Temporary prefabricated houses (PHs) can be effective in providing disaster victims with a temporary living place quickly whenever there is a natural disaster, and are also widely used in providing construction workers with living places. However, there are very limited studies on indoor thermal environment inside PHs, with their inadequacies. Therefore, an experimental study on the indoor thermal environments in an experimental PH located in the subtropics is reported in this paper. The study results suggested that at closed door and window situation, the air temperature inside the experimental PH was very high at daytime in summer, but very low at nighttime in winter. In addition, the variation of the air temperature inside the PH appeared synchronously with that of outdoor air temperature at daytime in summer, suggesting insignificant thermal mass of envelope to store solar heat gain. Furthermore, in both winter and summer, indoor air temperature stratification was observed. At daytime, indoor air temperature was increased with the height but at nighttime, decreased with the height. Finally, external roof temperatures in both winter and summer time were lower than outdoor air temperature, reflecting sky cooling effects for the experimental PH. The measured thermal environments inside the experimental PH, clearly demonstrated that the thermal environments inside PHs are highly unacceptable for long term occupation and that appropriate measures should be taken to improve the thermal environments in PHs.

Analysis of atmospheric turbulence in the upper layers of sea fog

Atmospheric turbulence plays a vital role in the formation and dissipation of fog. However, studies of such turbulence are typically limited to observations with ultrasonic anemometers less than 100 m above ground. Thus, the turbulence characteristics of upper fog layers are poorly known. In this paper, we present 4-layers of data, measured by ultrasonic anemometers on a wind tower about 400 m above the sea surface; we use these data to characterize atmospheric turbulence atop a heavy sea fog. Large differences in turbulence during the sea fog episode were recorded. Results showed that the kinetic energy, momentum flux, and sensible heat flux of turbulence increased rapidly during the onset of fog. After onset, high turbulence was observed within the uppermost fog layer. As long as this turbulence did not exceed a critical threshold, it was crucial to enhancing the cooling rate, and maintaining the fog. Vertical momentum flux and sensible heat flux generated by this turbulence weakened wind speed and decreased air temperature during the fog. Towards the end of the fog episode, the vertical distribution of sensible heat flux reversed, contributing to a downward momentum flux in all upper layers. Spatial and temporal scales of the turbulence eddy were greater before and after the fog, than during the fog episode. Turbulence energy was greatest in upper levels, around 430 m and 450 m above mean sea level (AMSL), than in lower levels of the fog (390 m and 410 m AMSL); turbulence energy peaked along the mean wind direction. Our results show that the status of turbulence was complicated within the fog; turbulence caused fluxes of momentum and sensible heat atop the fog layer, affecting the underlying fog by decreasing or increasing average wind speed, as well as promoting or demoting air temperature stratification.

Simulating buoyancy-driven airflow in buildings by coarse-grid fast fluid dynamics

Fast fluid dynamics (FFD) is an intermediate model between multi-zone models and computational fluid dynamics (CFD) models for indoor airflow simulations. The use of coarse grids is preferred with FFD in order to increase computing speed. However, by using a very large mesh cell to represent a heat source that could have a much smaller physical size than the cell, coarse-grid FFD would under-predict the thermal plume and thermal stratification. This investigation integrated a thermal plume model into coarse-grid FFD. The integration first used the plume model to calculate a source for the momentum equations and then corrected the temperature at the plume cell. The integration enabled coarse-grid FFD to correctly predict the plumes. When applied to displacement ventilation, coarse-grid FFD with the plume model can accurately predict the mean air temperature stratification in rooms as compared with experimental data from the literature. The improved model has also been used to calculate the ventilation rate for buoyancy-driven natural ventilation. The calculated ventilation rates agree well with the experimental data or predictions by CFD and analytical models. Coarse-grid FFD with the plume model used only a small fraction of the computing time required by fine-grid FFD, while the associated errors for the two grid sizes were comparable.

Sensitivity analysis of the thermal performance of radiant and convective terminals for cooling buildings

Heating and cooling terminals can be classified in two main categories: convective terminals (e.g. active chilled beam, air conditioning) and radiant terminals. The mode of heat transfer of the two emitters is different: the first one is mainly based on convection, whereas the second one is based on both radiation and convection. In order to characterise the advantages and drawbacks of the different terminals, steady-state simulations of a typical office room have been performed using four types of terminals (active chilled beam, radiant floor, wall and ceiling). A sensitivity analysis has been conducted to determine the parameters influencing their thermal performance the most. The air change rate, the outdoor temperature and the air temperature stratification have the largest effect on the cooling need (maintaining a constant operative temperature). For air change rates higher than 0.5 ACH, differences between terminals can be observed. Due to their higher dependency on the air change rate and outdoor temperature, convective terminals are generally less energy effective than radiant terminals. The global comfort level achieved by the different systems is always within the recommended range, but differences have been observed in the uniformity of comfort.