Numerical Simulation of Flow, Heat and Moisture Transfer in Heat and Moisture Exchanger (HME) Devices

2014 ◽  
Vol 553 ◽  
pp. 121-129
Author(s):  
Seyed Pezhman Payami ◽  
Masud Behnia ◽  
Barry Dixon ◽  
John Santamaria ◽  
Mehrdad Behnia

Heat and Moisture Exchanger (HME) is a simple solution to the problems of warming and humidification of inspired gases during ventilator treatment. The device acts as an “artificial” nose or passive humidifier, added to the breathing circuit to retain and exchange heat and moisture between inspiration and expiration. The HME traps expiratory heat and moisture from patient’s exhaled breath in a porous medium and returns a portion of them through the subsequent inspiratory cycle. The aim of our paper is to develop a computational fluid dynamics (CFD) model of an HME device commonly used in anaesthesia and intensive care. The CFD results allow a better understanding of flow behaviour leading to the design of more efficient devices. The CFD model solves the gas flow, heat and mass transfer equations in a DAR Hygrobac S (Mallinckrodt DAR, Mirandola, Italy). The temperature, absolute humidity and pressure fields are obtained during expiratory phase to evaluate heat and moisture conserving efficiencies and air flow resistance. The effect of flow rate as one of the major parameters in ventilator setting on temperature, humidity and pressure drop is determined. Inside the HME device, areas of recirculation are observed. As the flow rate increases the output temperature and absolute humidity go up causing a reduction in heat and moisture conserving capacities. Comparison of the CFD results with previously obtained experimental data shows a satisfactory agreement.

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Mohamed R. H. Abdel-Salam ◽  
Robert W. Besant ◽  
Carey J. Simonson

This paper presents performance definitions for calculating the overall effectiveness of three-fluid heat and moisture exchangers. The three-fluid heat and moisture exchanger considered in this paper is a combination of a liquid-to-liquid heat exchanger for heat transfer between a desiccant solution and a refrigerant and an energy exchanger for heat and moisture transfer between desiccant solution and air streams. The performance definitions presented in this paper are used to calculate the overall sensible and latent effectivenesses of a three-fluid heat and moisture exchanger, which has been tested under air cooling and dehumidifying operating conditions in a previous work (Abdel-Salam et al., 2016, “Design and Testing of a Novel 3-Fluid Liquid-to-Air Membrane Energy Exchanger (3-Fluid LAMEE),” Int. J. Heat Mass Transfer, 92, pp. 312–329). The effectiveness of this three-fluid heat and moisture exchanger is compared when calculated using the traditional energy exchanger effectiveness equations and the overall performance definitions. Results show that the overall performance definitions provide effectiveness values that are less sensitive to changes in the inlet refrigerant temperature and therefore are more generally applicable for energy exchanger design than the traditional effectiveness equations used in the literature.


1984 ◽  
Vol 63 (6) ◽  
pp. 566???570 ◽  
Author(s):  
Jack Chalon ◽  
Joseph P. Markham ◽  
Mahgul M. All ◽  
Sivam Ramanathan ◽  
Herman Turndorf

2014 ◽  
Vol 119 (4) ◽  
pp. 926-931 ◽  
Author(s):  
Gustavo P. Bicalho ◽  
Leandro G. Braz ◽  
Larissa S. B. de Jesus ◽  
Cesar M. C. Pedigone ◽  
Lídia R. de Carvalho ◽  
...  

1987 ◽  
Vol 15 (3) ◽  
pp. 317-322 ◽  
Author(s):  
M. J. Turtle ◽  
A. H. Ilsley ◽  
A. J. Rutten ◽  
W. B. Runciman

Six disposable heat and moisture exchangers were tested on patients undergoing anaesthesia requiring mechanical ventilation. Inspiratory humidity and temperature were monitored to find the steady-state values reached with each device together with the times taken for these to be achieved. The exchangers were tested in a non-rebreathing T-piece circuit and in a conventional circle system with a fresh gas flow of 6 l/min: the Siemens 150 provided 28 and 32 mg of water/litre of inspired gas (at about 30°C) in 10 and 5 min respectively, but is rather heavy and bulky. The Portex Humidvent provided 25 and 30 mg/l, and although taking longer to reach steady state (27 and 15 min respectively) is small, light and cheap. The Siemens 151 provided 25 and 27 mg/l in 18 and 10 min respectively, but is heavier than the Portex exchanger. The performances of these three devices were not significantly different from each other in either study (P < 0.05). For the T-piece system the Pall and Engstrom exchangers were the next most efficient. The Pall device provided 18 and 23 mg/l (in 18 and 8 min respectively) and the Engstrom provided 20 and 23 mg/l (in 19 and 10 min respectively). In the circle system, there were no significant differences between the peformances of the Portex, Siemens 151, Pall and Engstrom exchangers. The Pall is also a very effective bacterial filter and has been found to be satisfactory in the intensive care setting. The Terumo appeared to perform no better than a circle system with catheter mount (13 mg/l at 27°C). It would seem that more complex humidification equipment is not necessary during anaesthesia if an efficient heat and moisture exchanger is used.


2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Matteo Filippini ◽  
Mauro Serpelloni ◽  
Valeria Quaranta ◽  
Paolo Bellitti ◽  
Emilio Sardini ◽  
...  

Aim. To evaluate the conditioning capabilities of the DAR™ Hygrobac™ S, a Heat and Moisture Exchanger (HME), using a new device to measure the temperature (T) and the absolute humidity (AH) of the ventilated gases in vivo during mechanical ventilation in Intensive Care Unit (ICU) patients. Materials and Methods. In 49 mechanically ventilated ICU patients, we evaluated T and AH, indicating the HME efficacy, during the inspiratory phase upstream and downstream the HME and the ratio of inspired AH to expired AH and the difference between expired T and inspired T indicated the HME efficiency. Efficacy and efficiency were assessed at three time points: at baseline (t0, HME positioning time), at 12 hours (t1), and at 24 hours (t2) using a dedicated, ad hoc built wireless device. Differences over time were evaluated using one-way ANOVA for repeated measures, whereas differences between in vivo and laboratory values (declared by the manufacturer according to UNI® EN ISO 9360 international standard) were evaluated using one-sample Student t-test. Results. 49 HMEs were analysed in vivo during mechanical ventilation. T and AH means (SD) of the inspired gas (the efficacy) were 31.5°C (1.54) and 32.3 mg/l (2.60) at t0, 31.1°C (1.34) and 31.7 mg/l (2.26) at t1, and 31°C (1.29) and 31.4 mg/l (2.27) at t2. Both efficiency parameters were constant over time (inspired AH/expired AH=89%, p=0.24; and expired T–inspired T = 2.2°C, p=0.81). Compared with laboratory values, in vivo T and AH indicating efficacy were significantly lower (p<0.01), whereas the efficiency was significantly higher (p<0.01). Conclusions. HME performances can be accurately assessed for prolonged periods in vivo during routine mechanical ventilation in ICU patients. Temperature and absolute humidity of ventilated gases in vivo were maintained within the expected range and remained stable over time. HME efficacy and efficiency in vivo significantly differed from laboratory values.


1998 ◽  
Vol 18 (10) ◽  
pp. 769-771
Author(s):  
Tadahisa FUNAYAMA ◽  
Taro OHNO ◽  
Kiyoshi MIZUMOTO ◽  
Susumu FUJIOKA ◽  
Eiichi INADA ◽  
...  

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