Studies related to the effects of ambient temperature on the performance of an air conditioning unit have been carried out for decades. However, specific study concerning the effect of varied ambient temperature under constant relative humidity has not been reported yet. This paper discusses the operating conditions and performance of an air conditioner with R32 and nominal capacity of 2.6 kW. The test was carried out in a controlled psychrometric chamber under constant relative humidity of 50% and varied outdoor air temperature from 24 to 38°C. The increase of outdoor air temperature affects the operating conditions of the air conditioner. Generally, if the outdoor air temperature increases by 1°C the evaporating temperature increases by 0.27°C. Meanwhile, refrigerant suction temperature, discharge temperature, and condensing temperature increase by 0.08°C, 1.08°C, and 1.04°C, respectively. Under the same tests, the cooling capacity decreases by 1% and power consumption increases by 1.6%. In addition, the energy efficiency ratio of the air conditioner decreases by 2.1% per 1°C increase of outdoor air temperature.

ABSTRAKTelah dilakukan penelitian mengenai sifat penyerapan bunyi oleh bahan penyerap bunyi berbahan dasar Serat Batang Pisang (SBP) dengan matriks Polyester. Bahan Penyerap Bunyi yang dibuat dengan variasi komposisi fraksi volume yang berbeda, perbandingan fraksi volume SBP dan Polyester yang dibuat yaitu 30%:70%, 40%:60% dan 50%:50%. Metode penelitian dilakukan dalam tiga tahapan yaitu pengambilan serat batang pisang, pembuatan komposit dan pengujian sifat penyerapan bunyi komposit SBP. Pembuatan sampel diawali dengan pengambilan batang pisang, penguraian serat batang pisang, perlakuan alkali dengan NaOH 4 %, kemudian pencampuran SBP dengan matriksnya polyester. Pencetakan komposit dengan alat cetak tekan dengan penekanan 12 jam. Kemudian dilakukan uji karakterisasi sifat penyerapan bunyi. Uji penyerapan bunyi dilakukan dengan menggunakan signal generator dan sound level meter dengan mengacu pada prinsis metode tabung impedansi melalui pendekatan box akustik. Hasil penelitian komposit SBP Polyester mampu menyerap bunyi dengan koefisien serapan bunyi = 0,84 pada fraksi volume serat 50%, hal ini menunjukkan bahwa komposit SBP mampu menyerap bunyi dengan baik untuk frekuensi rendah dan frekuensi sedang, sesuai dengan standar ISO 11654:1997 (E) dimana koefisien serapan bunyi bahan akustik minimal sebesar = 0,15. ABSTRACTThis research conducted to find the physical properties of the absorption of sound from banana stem fiber (Serat Batang Pisang/SBP) with polyesters' matrix. The sound absorbent material made with a variety of different volume fraction composition. The comparison between the SBP and the volume fraction of the polyester is made of 30%: 70%, 40%: 60% and 50%: 50%. The method of research was done in three stages: making banana stem fiber, manufacturing composite and testing of composite SBP. Composite testing includes physical properties (sound absorption). Preparation of the samples started by taking a banana stem, decomposition banana stem fiber, alkali treatment with NaOH 4%, then mixing the SBP with the matrix polyester. Manufactured the composites by press the materials on the molding for 12 hours, then tested to find physical properties. Sound absorption test performed using a signal generator and a sound level meter with the principle of the impedance tube method through acoustic box approach as a reference. The results of the study showed that SBP with polyester composite capable to absorb the sound with sound absorption coefficient α = 0.84 at 50% fiber volume fraction. Thus SBP composites can absorb sound for low and medium frequency, based on the standard ISO 11654:1997 (E) where the minimum of sound absorption coefficient of acoustic materials is α = 0.15.

Flavonoid compound from durian shell biowaste was identified by phytochemical assay and FTIR spectrophotometric methods. Total flavonoid content determined by the aluminum chloride (AlCl3) method using a UV-Vis spectrophotometer. Durian shells, which are a waste that causes the environmental problem, can be used as a source of potentially valuable flavonoid compounds. Flavonoid has antioxidants ability that is beneficial and useful. Durian shell used in this research consists of three types, namely Malika, Malon, and Monti, which are from local Indonesian durian. Based on the result, proximate test analysis showed that three local durian shell samples generally had a water content of 7%, a fat content of 0.9%, the protein content of 4.9%, an ash content of 8.5%, and a 78% carbohydrate content. The results of the analysis of the three durian shell samples did not show significantly different results. Then for the phytochemical assay, three local durian shell samples contained phenols, steroids, and terpenoids, the results of the phytochemical assay showed that there were more phenolic groups than the flavonoid group. The following analysis result is the functional group of three samples using Fourier Transform Infrared (FT-IR) spectrophotometer shows that the three types of durian shell samples have a band that is slightly different from the standard, but the number of waves in this band is similar to the standard quercetin. Then for total flavonoid levels in local durian shell using the aluminum chloride (AlCl3) method, the result is Monti durian shell having higher flavonoid levels, each 0.405 ± 0.002 mg QE/g, compared with each other shell type namely Malika and Malon of 0.321 ± 0.003 mg QE / g and 0.324 ± 0.002 mg QE/g, respectively. Thus in this study shows that Indonesian local durian shell contains significant total flavonoid content without the need for extraction. Samples were only dissolved with ethanol solvent, then a series of tests were carried out, then a series of tests were carried out, ranging from phytochemical assessment, FTIR spectrophotometer, and AlCl3 methods to determine the total flavonoid content through quantitative.

Anthocyanin from the flower Ruelila tuberosa L was successfully extracted by maceration using methanol. The total extract obtained was 19.22% with a concentration of 1.503 mg/L correspondingly. Retention time was analyzed using Thin Layer Chromatography and an Rf value of 0.43 was achieved. The analytical determination of functional groups was conducted using FTIR. The sensitivity of anthocyanin towards phosphate buffer pH is 0.222 at the range of pH 6 - 8 with R2 = 0.996 at maximum wavelength of 635 nm. On the other hand, its sensitivity towards citrate buffer is 0.022 at pH range 6 - 8 with a linearity of R2 = 0.999 at 625 nm maximum wavelength. The anthocyanin showed good in sensitivity and dynamic range in 0.1 M Phosphate buffer solution.

Province of North Sumatera has been well known as a territory having multi kind of industrial minerals which have not been used and maintained properly and optimally. One of which is a natural Pahae zeolite derived from Tarutung, Tapanuli Utara-Indonesia. The objective of this research is to exploit Pahae zeolite to absorb water molecules flowing into the combustion chamber of a hydrogen fueled motorcycle. The generation of water molecules was as a result of water splitting process in water to hydrogen converter of the motorcycle. The grain size of Pahae zeolite was lessened up to 60 and 200 meshes which were then chemically activated by soaking with 30% KOH solution and calcination at a temperature of 300°C for 2 hours. The test results conducted on the intake pipe of combustion chamber showed that the particle size of 200 meshes had more absorption than that of 60 meshes. It was also found that type of Pahae zeolite had better absorption compared with Cikalong zeolite.