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Psychrometric Performance Testing for HVAC&R Components and Equipment
Published in Josua P. Meyer, Michel De Paepe, The Art of Measuring in the Thermal Sciences, 2020
Orkan Kurtulus, Christian K. Bach, Romit Maulik, Omer San, Davide Ziviani, Craig R. Bradshaw, Eckhard A. Groll
While typically less severe, failure of humidification controls can also lead to problems. It is recommended to use a limiting humidistat to shut off humidification above the room’s safe maximum humidity limits. This limiting humidistat should be located at a location where it can sense the humidity addition without fans in operation. As a passive and secondary safety mechanism, ductwork should be sloped with a drain at the lowest point to prevent filling ductwork with condensate until mechanical failure.
Refrigeration— Air Conditioning—Heating
Published in H. D. McGeorge, General Engineering Knowledge, 2012
Other systems Heating of the air may be by steam (as above), hot water circulation or electric heating elements. Cooling by chilled water or brine may be used instead of direct expansion. A humidistat can be installed for automatic humidity measurement and control.
Heating and Cooling
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
Humidifiers are sometimes added to warm air heating systems to reduce interior dryness and reduce fuel bills during the heating season. It is generally believed that a higher humidity can allow comfortable living at three degrees lower than would be required in a dryer environment. The principle behind this is the same one that makes 90°F in a humid summer environment (such as in Florida) feel much hotter than 90°F in a dry summer environment (such as in Las Vegas). Humidifiers are installed in the air distribution system and are controlled by a humidistat (usually located on or near the humidifier housing). A humidistat is an automatic control that switches a fan, humidifier, or dehumidifier on and off based on the relative humidity at the control. Humidifiers can be of several types: Pan type (Figure 9-38), where an open pan of water is used to provide water vapor to the circulating air stream.Stationary pad (Figure 9-36), where air is drawn from the furnace plenum or supply air duct by a fan, blown over an evaporator pad, and returned to the air distribution system.Revolving drum (Figure 9-35), where water from a small reservoir is picked up by a revolving pad and exposed to an air stream from the furnace plenum or supply ductwork.Atomizer (Figure 9-37), where water is broken into small particles by an atomizing device and released into the supply or return air ductwork.
Virucidal Efficacy of Gaseous Ozone Against Type 1 Herpes Simplex Virus (HSV-1)
Published in Ozone: Science & Engineering, 2023
Evans Ahortor, Les Baillie, David Lloyd, James Blaxland
To assist analysis, the chamber working area can be accessed via glove ports and a sealed hatch is in place for material transfer. Prior to any analysis, the chamber is extracted for 15 min (extract is to the external environment via a HEPA filter) inlet air is via a separate duct from the environment and is also HEPA filtered. The extract system is then sealed and five internal mixing fans at a fixed speed of 39.1 m3/h (RS components, UK) are activated and maintained for the duration of analysis. The humidity is then increased to the desired parameters and allowed to standardize for 30 min, humidity is maintained and controlled by a GAS sonic 10 L humidifier and Faran HR-DHTC humidistat. To generate ozone, the chamber is equipped with a 2B Tech 106-M ozone monitor (Colorado USA), which is UKAS calibrated (Ricardo, UK), Devilbiss 1025 oxygen concentrator (HCE, UK) and a Q5 ozone generator 10 g/h with PLC control 20 mA output (Ozone Industries Ltd, UK). Once the desired concentration of ozone is reached as displayed by the 106-M monitor, it is allowed to standardize for 30 min prior to the introduction of test materials. The concentration of ozone is maintained in the chamber via the 2B tech 106-M monitor and maintains ±0.1 ppm of the desired concentration throughout testing. Room ozone concentration is measured via the monitor at 5-s intervals throughout the test period.
Comparisons of load-based and AHRI 210/240 testing and rating for residential heat pumps
Published in Science and Technology for the Built Environment, 2023
Parveen Dhillon, W. Travis Horton, James E. Braun
In load-based cooling tests, a test unit’s performance is evaluated at two different sets of test conditions representing dry and humid climate types as shown in Table 1. In a load-based test, the indoor conditions represent the target comfort conditions which are set as the test unit thermostat and/or humidistat setpoint, whichever is applicable. For dry coil tests, only sensible building loads are simulated while keeping the indoor humidity levels low enough such that there is no dehumidification at the indoor unit cooling coil. Whereas, for humid test conditions, both sensible as well as latent loads are simulated, and test equipment sensible and latent cooling performance is measured. Similarly, for heating mode, equipment performance is measured at test conditions representative of two different climate types: continental and marine, as presented in Table 2. In heating load-based tests, only dynamic temperature variation of indoor test room conditions is considered as there is no dehumidification by the coil that can necessitate consideration of humidity response. Furthermore, at test conditions where the unit fails to maintain the indoor temperature to the target thermostat setpoint due to the maximum capacity being less than the building load, a full-load test is conducted. In a full-load test, indoor and outdoor test room conditions are maintained at a steady state and the equipment performance is measured by running it full-out at maximum capacity.
A review of desiccant evaporative cooling systems in hot and humid climates
Published in Advances in Building Energy Research, 2021
Ismanizam Abd Manaf, Faisal Durrani, Mahroo Eftekhari
The desiccant evaporative cooling technology is a combination of the desiccant dehumidifier and evaporative cooler. Evaporative cooling systems on their own are not recommended for hot and humid weather as they perform poorly in high humidity. To cater for the moisture content in the ambient air, a desiccant dehumidifier is combined with the evaporative cooling system. The evaporative cooling method was introduced in order to utilize the natural cooling effects of evaporation to cool buildings. There are many configurations of evaporative coolers (either direct or indirect) that are operated in ventilation or recirculation cycles. The only energy used in this DEC system is to drive the fans and water pump and to regenerate the desiccant dehumidifier during the regeneration process. This regeneration energy can be provided by any renewable, low-grade thermal energy source such as solar or waste heat. The sensible and latent loads can be controlled separately in this system using a humidistat and thermostat for the control of wet and dry bulb temperatures respectively. This system is a suitable alternative to mechanical vapour compression systems and can be efficiently used for air-conditioning applications with fewer power requirements (Mujahid Rafique et al., 2015). Therefore, this system is not only ideal for controlling temperature and humidity, but it is also great for saving energy, cost-effectiveness, simplicity and its low environmental impact.