Effectiveness - NTU data and analysis for air conditioning and refrigeration air coils

Navarro, Hélio Aparecido; Cabezas‐Gómez, Luben; Bastos, João R.; Filho, Zoghbi; Ribatski, Gherhardt; Saíz-Jabardo, José Maria

doi:10.1590/s1678-58782010000300004

Cited by 9 publications

(6 citation statements)

References 14 publications

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“…In fig. 1, number 1 is a simulation according to the method [17]; number 2 is according to (13) with the coefficients in Table I; number 3 is according to (13) with the average coefficients in Table II; number 4 is according to (7) for tubular heat exchangers [13]; number 5 is according to (8) for plate heat exchangers [13]; number 6 is according to (10) for the second stage of heater [16].…”

Section: Resultsmentioning

confidence: 99%

“…those NTU(t) will change according to the hyperbola law (line 1), which curves 2 and 3 reflect according to the (13). Relations (7), (8) and (10) are again inapplicable in this case, since they describe linear dependencies.…”

Section: Resultsmentioning

confidence: 99%

“…Thus the existing ratios are tied to a specific type of heat exchanger (design characteristics) (7), (8), or to the scheme of their operation (9), (10), do not describe the change of parameters in any variable modes (for example, at constant temperatures of heat carriers), which requires their refinement and clarification.…”

Section: Literature Reviewmentioning

confidence: 99%

“…To assess the efficiency of heat transfer processes in variable operating modes, the values used in the theory of heat exchangers are widely used, which include heat exchanger efficiency , log average temperature difference t, heat exchanger surface F and the number of heat transfer units NTU. These indicators are widely used for calculating and comparing the efficiency of heat exchangers of various types [1,2] in heat and power [3][4][5], aviation [6], chemical industry [7], in ventilation and air conditioning systems [8][9][10][11][12]. The convenience of using dimensionless complexes, such as NTU, is in the assumption that the heat transfer coefficient and the efficiency of the heat exchanger are practically independent of the temperatures of the heat exchanging media [13,14].…”

Section: Introductionmentioning

confidence: 99%

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Research of variable characteristics of heat exchange equipment

Rafalskaya

Rudyak

2019

E3S Web Conf.

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Heat exchangers used in various industries, most often work in conditions of variable flows and temperatures. At the same time, the existing theories of calculation of heat exchanger modes are based on the use of constant dimensionless parameters in any mode of operation. The purpose of this work is to obtain dependencies to determine the effect of coolant temperatures on the variable parameter of the heat exchanger. Using the simulation method, dependencies were found that describe the change in the heat exchanger parameter which made it possible to obtain a general formula for the change in the heat exchanger parameter at varying coolant temperatures. To test the applicability of the existing relations describing the change in the heat exchanger parameter and the formula obtained, a large number of heat exchangers were calculated in variable operating modes. Comparison with the simulation results showed that the ratios of the known theories of heat exchangers do not work in all modes and their application can lead to significant errors. A formula has been obtained allows one to find the effect of coolant temperatures on the variable parameter of the heat exchanger. The formula can be used to predict the modes of large systems.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Research of variable characteristics of heat exchange equipment

Rafalskaya

Rudyak

2019

E3S Web Conf.

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“…The basic idea of this novel concept is that the sensible and latent loads can be treated independently of a WSHE. According to the ε − NTU method2627, the sensible heat capacity of a WSHE as an evaporator, Q c , s , can be estimated, ignoring heat capacity loss due to its thermal inertia,…”

Section: Resultsmentioning

confidence: 99%

Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers

Wang

et al. 2017

Sci Rep

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Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8–3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump’s efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications.

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