The present work presents a new experimental study of the enhancement of turbulent
convection heat transfer inside tubes for combined thermal and hydrodynamic entry length of one
popular “turbulator” (twisted tape with width slightly less than internal tube diameter) inserted for
fire tube boilers. Cylindrical combustion chamber was used to burn (1.6 to 7kg/h) fuel oil #2 to
deliver hot gases with ranges of Reynolds number (10500 to 21700), and (11400 to 24150) for both
empty and inserted tube respectively.A uniform wall temperature technique was used by keeping
approximately constant water temperature difference (25ºC) between inlet and exit cooling water in
parallel flow shell and tube heat exchanger. The test tube consisted of smooth carbon steel tube of
(2400mm) long and (52mm) internal diameter. This test tube instrumented to derive local heat
transfer coefficient and local flue gasses static pressure.The experimental results show that for the
same fuel consumption, twisted tape insert with (H/D = 11.15) enhanced the mean Nusselt number
in (75.2%), (68.8%), (49.8%), (40.3%), and (16.7%) for fuel consumption (7kg/h), (6.16kg/h),
(4.5kg/h), (3.24kg/h), and (1.6kg/h) respectively.A set of empirical correlations that permit the
evaluation of the mean Nusselt number (for developing and fully developed region), and average
Nusselt number (for developed region) for empty and inserted tube are generated for engineering
applications.
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Theoretical spectroscopic studies of beryllium oxide has been carried out, potential energy curves for ground states X1Σ+ and exited states A1Π , B1Σ+ by using two functions Morse and and Varshni compared with experimental results. The potentials of this molecule are agreement with experimental results. The Fortrat Parabola corrcponding to and branches were determind in the range 1<J<20 for the (0-0) band. It was found that for electronic transition A1Π- X1Σ+ the bands head lies in branche of Fortrat p |
Background and Aim: due to the rapid growth of data communication and multimedia system applications, security becomes a critical issue in the communication and storage of images. This study aims to improve encryption and decryption for various types of images by decreasing time consumption and strengthening security. Methodology: An algorithm is proposed for encrypting images based on the Carlisle Adams and Stafford Tavares CAST block cipher algorithm with 3D and 2D logistic maps. A chaotic function that increases the randomness in the encrypted data and images, thereby breaking the relation sequence through the encryption procedure, is introduced. The time is decreased by using three secure and private S-Boxes rather than using si
... Show MoreThis study aimed to incorporate hydroxyapatite nanoparticles (nHA) or amorphous calcium phosphate nanoparticles (nACP) into a self-etch primer (SEP) to develop a simplified orthodontic bonding system with remineralizing and enamel preserving properties.
nHA and nACP were incorporated into a commercial SEP (Transbond™ plus) in 7% weight ratio and compared with the plain SEP as a control. Shear bond strengths (SBS), enamel damage, and adhesive remnant index (ARI) scores were evaluated at 24 h
Shumblan (SH) is one of the most undesirable aquatic plants widespread in the irrigation channels and water bodies. This work focuses on boosting the biogas potential of shumblan by co-digesting it with other types of wastes without employing any chemical or thermal pretreatments as done in previous studies. A maximum biogas recovery of 378 ml/g VS was reached using shumblan with cow manure as inoculum in a ratio of 1:1. The methane content of the biogas was 55%. Based on volatile solid (VS) and C/N ratios, biogas productions of 518, 434, and 580 ml/g VS were obtained when the shumblan was co-digested with food wastes (SH:F), paper wastes (SH:P), and green wastes (SH:G) respectively. No significant changes of methane contents were observ
... Show MoreLaurylamine hydrochloride CH3(CH2)11 NH3 – Cl has been chosen from cationic surfactants to produce secondary oil using lab. model shown in fig. (1). The relationship between interfacial tension and (temperature, salinity and solution concentration) have been studied as shown in fig. (2, 3, 4) respectively. The optimum values of these three variables are taken (those values that give the lowest interfacial tension). Saturation, permeability and porosity are measured in the lab. The primary oil recovery was displaced by water injection until no more oil can be obtained, then laurylamine chloride is injected as a secondary oil recovery. The total oil recovery is 96.6% or 88.8% of the residual oil has been recovered by this technique as shown
... Show MoreThe services provided by the municipal institutions of the basic things needed by the man in his daily life and the evolution of cities basically depends on these services and therefore has paid most of the world's attention to this vital facility and give him the biggest concern for the welfare of the citizens, as is the research problem that there is no program scrutiny to evaluate the performance of municipal institutions contribute to measuring the efficiency and effectiveness of the services provided and was based on research on the premise that the preparation of the existence of audit program to evaluate the performance of municipal institutions contribute to measuring the efficiency and effectiveness of services provided has reac
... Show MoreThe study aimed to prepare quick response codes to learn some of the technical skills of the second graders in the Faculty of Physical Education and Sports Sciences. The experimental method was used in the design of the experimental and control experimental and control groups. The research sample was represented by second-graders in the College of Physical Education and Sports Sciences / University of Baghdad, and by lot, the second division (a) was chosen to represent the experimental group that applied the inverse method using the QR code, and the second division (g) to represent the control group and applied the traditional method. (10) Students per group. After the tribal tests, his main experiment was carried out for 10 weeks with one
... Show MoreBackground: Breast Cancer is the most common malignancy among the Iraqi population; the majority of cases are still diagnosed at advanced stages with poor prospects of cure. Early detection through promoting public awareness is one of the promising tools in its control. Objectives: To evaluate the baseline needs for breast cancer awareness in Iraq through exploring level of knowledge, beliefs and behavior towards the disease and highlighting barriers to screening among a sample of Iraqi women complaining of breast cancer. Methodology: Two-hundred samples were enrolled in this study; gathered from the National